diff --git a/card-functionality/src/tests.rs b/card-functionality/src/tests.rs
index 004625d..02c4b18 100644
--- a/card-functionality/src/tests.rs
+++ b/card-functionality/src/tests.rs
@@ -15,7 +15,7 @@ use sequoia_openpgp::Cert;
 use openpgp_card;
 use openpgp_card::algorithm::AlgoSimple;
 use openpgp_card::card_do::{KeyGenerationTime, Sex};
-use openpgp_card::{CardClient, Error, KeyType, StatusBytes};
+use openpgp_card::{CardTransaction, Error, KeyType, StatusBytes};
 use openpgp_card_sequoia::card::Open;
 use openpgp_card_sequoia::util::{
     make_cert, public_key_material_to_key, public_to_fingerprint,
@@ -53,7 +53,7 @@ pub enum TestError {
 
 /// Run after each "upload keys", if key *was* uploaded (?)
 pub fn test_decrypt(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     param: &[&str],
 ) -> Result<TestOutput, TestError> {
     assert_eq!(
@@ -65,12 +65,12 @@ pub fn test_decrypt(
     let cert = Cert::from_str(param[0])?;
     let msg = param[1].to_string();
 
-    card_client.verify_pw1("123456")?;
+    card_tx.verify_pw1("123456")?;
 
     let p = StandardPolicy::new();
 
     let res = openpgp_card_sequoia::util::decrypt(
-        card_client,
+        card_tx,
         &cert,
         msg.into_bytes(),
         &p,
@@ -84,21 +84,18 @@ pub fn test_decrypt(
 
 /// Run after each "upload keys", if key *was* uploaded (?)
 pub fn test_sign(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     param: &[&str],
 ) -> Result<TestOutput, TestError> {
     assert_eq!(param.len(), 1, "test_sign needs a filename for 'cert'");
 
-    card_client.verify_pw1_for_signing("123456")?;
+    card_tx.verify_pw1_for_signing("123456")?;
 
     let cert = Cert::from_str(param[0])?;
 
     let msg = "Hello world, I am signed.";
-    let sig = openpgp_card_sequoia::util::sign(
-        card_client,
-        &cert,
-        &mut msg.as_bytes(),
-    )?;
+    let sig =
+        openpgp_card_sequoia::util::sign(card_tx, &cert, &mut msg.as_bytes())?;
 
     // validate sig
     assert!(util::verify_sig(&cert, msg.as_bytes(), sig.as_bytes())?);
@@ -107,10 +104,10 @@ pub fn test_sign(
 }
 
 fn check_key_upload_metadata(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     meta: &[(String, KeyGenerationTime)],
 ) -> Result<()> {
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
 
     // check fingerprints
     let card_fp = ard.fingerprints()?;
@@ -151,10 +148,10 @@ fn check_key_upload_algo_attrs() -> Result<()> {
 }
 
 pub fn test_print_caps(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
 
     let aid = ard.application_id()?;
     println!("aid: {:#x?}", aid);
@@ -172,17 +169,17 @@ pub fn test_print_caps(
 }
 
 pub fn test_print_algo_info(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
 
     let dec = ard.algorithm_attributes(KeyType::Decryption)?;
     println!("Current algorithm for the decrypt slot: {}", dec);
 
     println!();
 
-    let algo = card_client.algorithm_information();
+    let algo = card_tx.algorithm_information();
     if let Ok(Some(algo)) = algo {
         println!("Card algorithm list:\n{}", algo);
     }
@@ -191,7 +188,7 @@ pub fn test_print_algo_info(
 }
 
 pub fn test_upload_keys(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     param: &[&str],
 ) -> Result<TestOutput, TestError> {
     assert_eq!(
@@ -200,16 +197,16 @@ pub fn test_upload_keys(
         "test_upload_keys needs a filename for 'cert'"
     );
 
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
     let cert = Cert::from_file(param[0])?;
 
     let p = StandardPolicy::new();
 
-    let meta = util::upload_subkeys(card_client, &cert, &p)
+    let meta = util::upload_subkeys(card_tx, &cert, &p)
         .map_err(|e| TestError::KeyUploadError(param[0].to_string(), e))?;
 
-    check_key_upload_metadata(card_client, &meta)?;
+    check_key_upload_metadata(card_tx, &meta)?;
 
     // FIXME: implement
     check_key_upload_algo_attrs()?;
@@ -219,10 +216,10 @@ pub fn test_upload_keys(
 
 /// Generate keys for each of the three KeyTypes
 pub fn test_keygen(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
     // Generate all three subkeys on card
     let algo = param[0];
@@ -230,7 +227,7 @@ pub fn test_keygen(
     let alg = AlgoSimple::try_from(algo)?;
 
     println!(" Generate subkey for Signing");
-    let (pkm, ts) = card_client.generate_key_simple(
+    let (pkm, ts) = card_tx.generate_key_simple(
         public_to_fingerprint,
         KeyType::Signing,
         alg,
@@ -238,7 +235,7 @@ pub fn test_keygen(
     let key_sig = public_key_material_to_key(&pkm, KeyType::Signing, ts)?;
 
     println!(" Generate subkey for Decryption");
-    let (pkm, ts) = card_client.generate_key_simple(
+    let (pkm, ts) = card_tx.generate_key_simple(
         public_to_fingerprint,
         KeyType::Decryption,
         alg,
@@ -246,7 +243,7 @@ pub fn test_keygen(
     let key_dec = public_key_material_to_key(&pkm, KeyType::Decryption, ts)?;
 
     println!(" Generate subkey for Authentication");
-    let (pkm, ts) = card_client.generate_key_simple(
+    let (pkm, ts) = card_tx.generate_key_simple(
         public_to_fingerprint,
         KeyType::Authentication,
         alg,
@@ -255,7 +252,7 @@ pub fn test_keygen(
         public_key_material_to_key(&pkm, KeyType::Authentication, ts)?;
 
     // Generate a Cert for this set of generated keys
-    let mut open = Open::new(card_client)?;
+    let mut open = Open::new(card_tx)?;
     let cert = make_cert(
         &mut open,
         key_sig,
@@ -273,15 +270,15 @@ pub fn test_keygen(
 
 /// Construct public key based on data from the card
 pub fn test_get_pub(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
     let key_gen = ard.key_generation_times()?;
 
     // --
 
-    let sig = card_client.public_key(KeyType::Signing)?;
+    let sig = card_tx.public_key(KeyType::Signing)?;
     let ts = key_gen.signature().unwrap().get().into();
     let key = public_key_material_to_key(&sig, KeyType::Signing, ts)?;
 
@@ -289,7 +286,7 @@ pub fn test_get_pub(
 
     // --
 
-    let dec = card_client.public_key(KeyType::Decryption)?;
+    let dec = card_tx.public_key(KeyType::Decryption)?;
     let ts = key_gen.decryption().unwrap().get().into();
     let key = public_key_material_to_key(&dec, KeyType::Decryption, ts)?;
 
@@ -297,7 +294,7 @@ pub fn test_get_pub(
 
     // --
 
-    let auth = card_client.public_key(KeyType::Authentication)?;
+    let auth = card_tx.public_key(KeyType::Authentication)?;
     let ts = key_gen.authentication().unwrap().get().into();
     let key = public_key_material_to_key(&auth, KeyType::Authentication, ts)?;
 
@@ -312,10 +309,10 @@ pub fn test_get_pub(
 }
 
 pub fn test_reset(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    let _res = card_client.factory_reset()?;
+    let _res = card_tx.factory_reset()?;
     Ok(vec![])
 }
 
@@ -325,25 +322,25 @@ pub fn test_reset(
 /// Returns an empty TestOutput, throws errors for unexpected Status codes
 /// and for unequal field values.
 pub fn test_set_user_data(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
     // name
-    card_client.set_name(b"Bar<<Foo")?;
+    card_tx.set_name(b"Bar<<Foo")?;
 
     // lang
-    card_client.set_lang(&[['d', 'e'].into(), ['e', 'n'].into()])?;
+    card_tx.set_lang(&[['d', 'e'].into(), ['e', 'n'].into()])?;
 
     // sex
-    card_client.set_sex(Sex::Female)?;
+    card_tx.set_sex(Sex::Female)?;
 
     // url
-    card_client.set_url(b"https://duckduckgo.com/")?;
+    card_tx.set_url(b"https://duckduckgo.com/")?;
 
     // read all the fields back again, expect equal data
-    let ch = card_client.cardholder_related_data()?;
+    let ch = card_tx.cardholder_related_data()?;
 
     assert_eq!(ch.name().as_deref(), Some("Bar<<Foo".as_bytes()));
     assert_eq!(
@@ -352,54 +349,54 @@ pub fn test_set_user_data(
     );
     assert_eq!(ch.sex(), Some(Sex::Female));
 
-    let url = card_client.url()?;
+    let url = card_tx.url()?;
     assert_eq!(&url, b"https://duckduckgo.com/");
 
     Ok(vec![])
 }
 
 pub fn test_private_data(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
     let out = vec![];
 
     println!();
 
-    let d = card_client.private_use_do(1)?;
+    let d = card_tx.private_use_do(1)?;
     println!("data 1 {:?}", d);
 
-    card_client.verify_pw1("123456")?;
+    card_tx.verify_pw1("123456")?;
 
-    card_client.set_private_use_do(1, "Foo bar1!".as_bytes().to_vec())?;
-    card_client.set_private_use_do(3, "Foo bar3!".as_bytes().to_vec())?;
+    card_tx.set_private_use_do(1, "Foo bar1!".as_bytes().to_vec())?;
+    card_tx.set_private_use_do(3, "Foo bar3!".as_bytes().to_vec())?;
 
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
-    card_client.set_private_use_do(2, "Foo bar2!".as_bytes().to_vec())?;
-    card_client.set_private_use_do(4, "Foo bar4!".as_bytes().to_vec())?;
+    card_tx.set_private_use_do(2, "Foo bar2!".as_bytes().to_vec())?;
+    card_tx.set_private_use_do(4, "Foo bar4!".as_bytes().to_vec())?;
 
-    let d = card_client.private_use_do(1)?;
+    let d = card_tx.private_use_do(1)?;
     println!("data 1 {:?}", d);
-    let d = card_client.private_use_do(2)?;
+    let d = card_tx.private_use_do(2)?;
     println!("data 2 {:?}", d);
-    let d = card_client.private_use_do(3)?;
+    let d = card_tx.private_use_do(3)?;
     println!("data 3 {:?}", d);
-    let d = card_client.private_use_do(4)?;
+    let d = card_tx.private_use_do(4)?;
     println!("data 4 {:?}", d);
 
     Ok(out)
 }
 
 // pub fn test_cardholder_cert(
-//     card_client: &mut (dyn CardClient + Send + Sync),
+//     card_tx: &mut (dyn CardTransaction + Send + Sync),
 //     _param: &[&str],
 // ) -> Result<TestOutput, TestError> {
 //     let mut out = vec![];
 //
 //     println!();
 //
-//     match card_client.cardholder_certificate() {
+//     match card_tx.cardholder_certificate() {
 //         Ok(res) => {
 //             out.push(TestResult::Text(format!("got cert {:x?}", res.data())))
 //         }
@@ -412,11 +409,11 @@ pub fn test_private_data(
 //         }
 //     };
 //
-//     card_client.verify_pw3("12345678")?;
+//     card_tx.verify_pw3("12345678")?;
 //
 //     let data = "Foo bar baz!".as_bytes();
 //
-//     match card_client.set_cardholder_certificate(data.to_vec()) {
+//     match card_tx.set_cardholder_certificate(data.to_vec()) {
 //         Ok(_resp) => out.push(TestResult::Text("set cert ok".to_string())),
 //         Err(e) => {
 //             out.push(TestResult::Text(format!(
@@ -427,7 +424,7 @@ pub fn test_private_data(
 //         }
 //     }
 //
-//     let res = card_client.cardholder_certificate()?;
+//     let res = card_tx.cardholder_certificate()?;
 //     out.push(TestResult::Text("get cert ok".to_string()));
 //
 //     if res.data() != data {
@@ -440,7 +437,7 @@ pub fn test_private_data(
 //
 //     // try using slot 2
 //
-//     match card_client.select_data(2, &[0x7F, 0x21]) {
+//     match card_tx.select_data(2, &[0x7F, 0x21]) {
 //         Ok(_res) => out.push(TestResult::Text("select_data ok".to_string())),
 //         Err(e) => {
 //             out.push(TestResult::Text(format!("select_data: {:?}", e)));
@@ -452,24 +449,24 @@ pub fn test_private_data(
 // }
 
 pub fn test_pw_status(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
     let out = vec![];
 
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
     let mut pws = ard.pw_status_bytes()?;
 
     println!("pws {:?}", pws);
 
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
     pws.set_pw1_cds_valid_once(false);
     pws.set_pw1_pin_block(true);
 
-    card_client.set_pw_status_bytes(&pws, false)?;
+    card_tx.set_pw_status_bytes(&pws, false)?;
 
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
     let pws = ard.pw_status_bytes()?;
     println!("pws {:?}", pws);
 
@@ -480,7 +477,7 @@ pub fn test_pw_status(
 /// - verify pw3 (check) -> Status
 /// - verify pw1 (check) -> Status
 pub fn test_verify(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
     // Steps:
@@ -498,7 +495,7 @@ pub fn test_verify(
     let mut out = vec![];
 
     // try to set name without verify, assert result is not ok!
-    let res = card_client.set_name("Notverified<<Hello".as_bytes());
+    let res = card_tx.set_name("Notverified<<Hello".as_bytes());
 
     if let Err(Error::CardStatus(s)) = res {
         assert_eq!(s, StatusBytes::SecurityStatusNotSatisfied);
@@ -506,9 +503,9 @@ pub fn test_verify(
         panic!("Status should be 'SecurityStatusNotSatisfied'");
     }
 
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
-    match card_client.check_pw3() {
+    match card_tx.check_pw3() {
         Err(Error::CardStatus(s)) => {
             // e.g. yubikey5 returns an error status!
             out.push(TestResult::Status(s));
@@ -519,17 +516,17 @@ pub fn test_verify(
         Ok(_) => out.push(TestResult::StatusOk),
     }
 
-    card_client.set_name(b"Admin<<Hello")?;
+    card_tx.set_name(b"Admin<<Hello")?;
 
-    let cardholder = card_client.cardholder_related_data()?;
+    let cardholder = card_tx.cardholder_related_data()?;
     assert_eq!(
         cardholder.name().as_deref(),
         Some("Admin<<Hello".as_bytes())
     );
 
-    card_client.verify_pw1("123456")?;
+    card_tx.verify_pw1("123456")?;
 
-    match card_client.check_pw3() {
+    match card_tx.check_pw3() {
         Err(Error::CardStatus(s)) => {
             // e.g. yubikey5 returns an error status!
             out.push(TestResult::Status(s));
@@ -540,16 +537,16 @@ pub fn test_verify(
         Ok(_) => out.push(TestResult::StatusOk),
     }
 
-    card_client.set_name(b"There<<Hello")?;
+    card_tx.set_name(b"There<<Hello")?;
 
-    let cardholder = card_client.cardholder_related_data()?;
+    let cardholder = card_tx.cardholder_related_data()?;
     assert_eq!(cardholder.name(), Some("There<<Hello".as_bytes()));
 
     Ok(out)
 }
 
 pub fn test_change_pw(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
     let out = vec![];
@@ -557,20 +554,20 @@ pub fn test_change_pw(
     // first do admin-less pw1 on gnuk
     // (NOTE: Gnuk requires a key to be loaded before allowing pw changes!)
     println!("change pw1");
-    card_client.change_pw1("123456", "abcdef00")?;
+    card_tx.change_pw1("123456", "abcdef00")?;
 
     // also set admin pw, which means pw1 is now only user-pw again, on gnuk
     println!("change pw3");
     // ca.change_pw3("abcdef00", "abcdefgh")?; // gnuk
-    card_client.change_pw3("12345678", "abcdefgh")?;
+    card_tx.change_pw3("12345678", "abcdefgh")?;
 
     println!("change pw1");
-    card_client.change_pw1("abcdef00", "abcdef")?; // gnuk
+    card_tx.change_pw1("abcdef00", "abcdef")?; // gnuk
 
     // ca.change_pw1("123456", "abcdef")?;
 
     println!("verify bad pw1");
-    match card_client.verify_pw1("123456ab") {
+    match card_tx.verify_pw1("123456ab") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
@@ -581,10 +578,10 @@ pub fn test_change_pw(
     }
 
     println!("verify good pw1");
-    card_client.verify_pw1("abcdef")?;
+    card_tx.verify_pw1("abcdef")?;
 
     println!("verify bad pw3");
-    match card_client.verify_pw3("00000000") {
+    match card_tx.verify_pw3("00000000") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
@@ -595,34 +592,34 @@ pub fn test_change_pw(
     }
 
     println!("verify good pw3");
-    card_client.verify_pw3("abcdefgh")?;
+    card_tx.verify_pw3("abcdefgh")?;
 
     println!("change pw3 back to default");
-    card_client.change_pw3("abcdefgh", "12345678")?;
+    card_tx.change_pw3("abcdefgh", "12345678")?;
 
     println!("change pw1 back to default");
-    card_client.change_pw1("abcdef", "123456")?;
+    card_tx.change_pw1("abcdef", "123456")?;
 
     Ok(out)
 }
 
 pub fn test_reset_retry_counter(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     _param: &[&str],
 ) -> Result<TestOutput, TestError> {
     let out = vec![];
 
     // set pw3, then pw1 (to bring gnuk into non-admin mode)
     println!("set pw3");
-    card_client.change_pw3("12345678", "12345678")?;
+    card_tx.change_pw3("12345678", "12345678")?;
     println!("set pw1");
-    card_client.change_pw1("123456", "123456")?;
+    card_tx.change_pw1("123456", "123456")?;
 
     println!("break pw1");
-    let _ = card_client.verify_pw1("wrong0");
-    let _ = card_client.verify_pw1("wrong0");
-    let _ = card_client.verify_pw1("wrong0");
-    let res = card_client.verify_pw1("wrong0");
+    let _ = card_tx.verify_pw1("wrong0");
+    let _ = card_tx.verify_pw1("wrong0");
+    let _ = card_tx.verify_pw1("wrong0");
+    let res = card_tx.verify_pw1("wrong0");
 
     match res {
         Err(Error::CardStatus(StatusBytes::AuthenticationMethodBlocked)) => {
@@ -643,23 +640,23 @@ pub fn test_reset_retry_counter(
     }
 
     println!("verify pw3");
-    card_client.verify_pw3("12345678")?;
+    card_tx.verify_pw3("12345678")?;
 
     println!("set resetting code");
-    card_client.set_resetting_code("abcdefgh".as_bytes().to_vec())?;
+    card_tx.set_resetting_code("abcdefgh".as_bytes().to_vec())?;
 
     println!("reset retry counter");
     // ca.reset_retry_counter_pw1("abcdef".as_bytes().to_vec(), None)?;
-    let _res = card_client.reset_retry_counter_pw1(
+    let _res = card_tx.reset_retry_counter_pw1(
         "abcdef".as_bytes().to_vec(),
         Some("abcdefgh".as_bytes().to_vec()),
     );
 
     println!("verify good pw1");
-    card_client.verify_pw1("abcdef")?;
+    card_tx.verify_pw1("abcdef")?;
 
     println!("verify bad pw1");
-    match card_client.verify_pw1("00000000") {
+    match card_tx.verify_pw1("00000000") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
@@ -675,7 +672,7 @@ pub fn test_reset_retry_counter(
 pub fn run_test(
     tc: &mut TestCardData,
     t: fn(
-        &mut (dyn CardClient + Send + Sync),
+        &mut (dyn CardTransaction + Send + Sync),
         &[&str],
     ) -> Result<TestOutput, TestError>,
     param: &[&str],
diff --git a/card-functionality/src/util.rs b/card-functionality/src/util.rs
index e9209c3..d351ccb 100644
--- a/card-functionality/src/util.rs
+++ b/card-functionality/src/util.rs
@@ -17,14 +17,14 @@ use sequoia_openpgp::serialize::stream::{
 use sequoia_openpgp::Cert;
 
 use openpgp_card::card_do::KeyGenerationTime;
-use openpgp_card::{CardClient, KeyType};
+use openpgp_card::{CardTransaction, KeyType};
 use openpgp_card_sequoia::sq_util;
 use openpgp_card_sequoia::util::vka_as_uploadable_key;
 
 pub const SP: &StandardPolicy = &StandardPolicy::new();
 
 pub(crate) fn upload_subkeys(
-    card_client: &mut dyn CardClient,
+    card_tx: &mut dyn CardTransaction,
     cert: &Cert,
     policy: &dyn Policy,
 ) -> Result<Vec<(String, KeyGenerationTime)>> {
@@ -49,7 +49,7 @@ pub(crate) fn upload_subkeys(
 
             // upload key
             let cuk = vka_as_uploadable_key(vka, None);
-            card_client.key_import(cuk, *kt)?;
+            card_tx.key_import(cuk, *kt)?;
         }
     }
 
diff --git a/openpgp-card-sequoia/src/card.rs b/openpgp-card-sequoia/src/card.rs
index 8eddd33..ecaf220 100644
--- a/openpgp-card-sequoia/src/card.rs
+++ b/openpgp-card-sequoia/src/card.rs
@@ -16,7 +16,7 @@ use openpgp_card::card_do::{
     ExtendedCapabilities, ExtendedLengthInfo, Fingerprint, HistoricalBytes,
     KeyGenerationTime, Lang, PWStatusBytes, SecuritySupportTemplate, Sex,
 };
-use openpgp_card::{CardClient, Error, KeySet, KeyType, Response};
+use openpgp_card::{CardTransaction, Error, KeySet, KeyType, Response};
 
 use crate::decryptor::CardDecryptor;
 use crate::signer::CardSigner;
@@ -27,7 +27,7 @@ use openpgp_card::crypto_data::PublicKeyMaterial;
 /// Representation of an opened OpenPGP card in its base state (i.e. no
 /// passwords have been verified, default authorization applies).
 pub struct Open<'a> {
-    card_client: &'a mut (dyn CardClient + Send + Sync),
+    card_tx: &'a mut (dyn CardTransaction + Send + Sync),
 
     // Cache of "application related data".
     //
@@ -47,12 +47,12 @@ pub struct Open<'a> {
 
 impl<'a> Open<'a> {
     pub fn new(
-        card_client: &'a mut (dyn CardClient + Send + Sync),
+        card_tx: &'a mut (dyn CardTransaction + Send + Sync),
     ) -> Result<Self, Error> {
-        let ard = card_client.application_related_data()?;
+        let ard = card_tx.application_related_data()?;
 
         Ok(Self {
-            card_client,
+            card_tx,
             ard,
             pw1: false,
             pw1_sign: false,
@@ -60,15 +60,15 @@ impl<'a> Open<'a> {
         })
     }
     pub fn feature_pinpad_verify(&mut self) -> bool {
-        self.card_client.feature_pinpad_verify()
+        self.card_tx.feature_pinpad_verify()
     }
 
     pub fn feature_pinpad_modify(&mut self) -> bool {
-        self.card_client.feature_pinpad_modify()
+        self.card_tx.feature_pinpad_modify()
     }
 
     pub fn verify_user(&mut self, pin: &str) -> Result<(), Error> {
-        let _ = self.card_client.verify_pw1(pin)?;
+        let _ = self.card_tx.verify_pw1(pin)?;
         self.pw1 = true;
         Ok(())
     }
@@ -79,13 +79,13 @@ impl<'a> Open<'a> {
     ) -> Result<(), Error> {
         prompt();
 
-        let _ = self.card_client.verify_pw1_pinpad()?;
+        let _ = self.card_tx.verify_pw1_pinpad()?;
         self.pw1 = true;
         Ok(())
     }
 
     pub fn verify_user_for_signing(&mut self, pin: &str) -> Result<(), Error> {
-        let _ = self.card_client.verify_pw1_for_signing(pin)?;
+        let _ = self.card_tx.verify_pw1_for_signing(pin)?;
 
         // FIXME: depending on card mode, pw1_sign is only usable once
 
@@ -99,7 +99,7 @@ impl<'a> Open<'a> {
     ) -> Result<(), Error> {
         prompt();
 
-        let _ = self.card_client.verify_pw1_for_signing_pinpad()?;
+        let _ = self.card_tx.verify_pw1_for_signing_pinpad()?;
 
         // FIXME: depending on card mode, pw1_sign is only usable once
 
@@ -108,7 +108,7 @@ impl<'a> Open<'a> {
     }
 
     pub fn verify_admin(&mut self, pin: &str) -> Result<(), Error> {
-        let _ = self.card_client.verify_pw3(pin)?;
+        let _ = self.card_tx.verify_pw3(pin)?;
         self.pw3 = true;
         Ok(())
     }
@@ -119,7 +119,7 @@ impl<'a> Open<'a> {
     ) -> Result<(), Error> {
         prompt();
 
-        let _ = self.card_client.verify_pw3_pinpad()?;
+        let _ = self.card_tx.verify_pw3_pinpad()?;
         self.pw3 = true;
         Ok(())
     }
@@ -128,14 +128,14 @@ impl<'a> Open<'a> {
     ///
     /// NOTE: on some cards this functionality seems broken.
     pub fn check_user_verified(&mut self) -> Result<Response, Error> {
-        self.card_client.check_pw1()
+        self.card_tx.check_pw1()
     }
 
     /// Ask the card if the admin password has been successfully verified.
     ///
     /// NOTE: on some cards this functionality seems broken.
     pub fn check_admin_verified(&mut self) -> Result<Response, Error> {
-        self.card_client.check_pw3()
+        self.card_tx.check_pw3()
     }
 
     pub fn change_user_pin(
@@ -143,7 +143,7 @@ impl<'a> Open<'a> {
         old: &str,
         new: &str,
     ) -> Result<Response, Error> {
-        self.card_client.change_pw1(old, new)
+        self.card_tx.change_pw1(old, new)
     }
 
     pub fn change_user_pin_pinpad(
@@ -151,7 +151,7 @@ impl<'a> Open<'a> {
         prompt: &dyn Fn(),
     ) -> Result<Response, Error> {
         prompt();
-        self.card_client.change_pw1_pinpad()
+        self.card_tx.change_pw1_pinpad()
     }
 
     pub fn reset_user_pin(
@@ -159,7 +159,7 @@ impl<'a> Open<'a> {
         rst: &str,
         new: &str,
     ) -> Result<Response, Error> {
-        self.card_client
+        self.card_tx
             .reset_retry_counter_pw1(new.into(), Some(rst.into()))
     }
 
@@ -168,7 +168,7 @@ impl<'a> Open<'a> {
         old: &str,
         new: &str,
     ) -> Result<Response, Error> {
-        self.card_client.change_pw3(old, new)
+        self.card_tx.change_pw3(old, new)
     }
 
     pub fn change_admin_pin_pinpad(
@@ -176,7 +176,7 @@ impl<'a> Open<'a> {
         prompt: &dyn Fn(),
     ) -> Result<Response, Error> {
         prompt();
-        self.card_client.change_pw3_pinpad()
+        self.card_tx.change_pw3_pinpad()
     }
 
     /// Get a view of the card authenticated for "User" commands.
@@ -296,21 +296,21 @@ impl<'a> Open<'a> {
     // --- URL (5f50) ---
 
     pub fn url(&mut self) -> Result<String> {
-        Ok(String::from_utf8_lossy(&self.card_client.url()?).to_string())
+        Ok(String::from_utf8_lossy(&self.card_tx.url()?).to_string())
     }
 
     // --- cardholder related data (65) ---
     pub fn cardholder_related_data(
         &mut self,
     ) -> Result<CardholderRelatedData> {
-        self.card_client.cardholder_related_data()
+        self.card_tx.cardholder_related_data()
     }
 
     // --- security support template (7a) ---
     pub fn security_support_template(
         &mut self,
     ) -> Result<SecuritySupportTemplate> {
-        self.card_client.security_support_template()
+        self.card_tx.security_support_template()
     }
 
     // DO "Algorithm Information" (0xFA)
@@ -324,12 +324,12 @@ impl<'a> Open<'a> {
             return Ok(None);
         }
 
-        self.card_client.algorithm_information()
+        self.card_tx.algorithm_information()
     }
 
     /// Firmware Version, YubiKey specific (?)
     pub fn firmware_version(&mut self) -> Result<Vec<u8>> {
-        self.card_client.firmware_version()
+        self.card_tx.firmware_version()
     }
 
     // ----------
@@ -338,14 +338,14 @@ impl<'a> Open<'a> {
         &mut self,
         key_type: KeyType,
     ) -> Result<PublicKeyMaterial> {
-        self.card_client.public_key(key_type).map_err(|e| e.into())
+        self.card_tx.public_key(key_type).map_err(|e| e.into())
     }
 
     // ----------
 
     /// Delete all state on this OpenPGP card
     pub fn factory_reset(&mut self) -> Result<()> {
-        self.card_client.factory_reset()
+        self.card_tx.factory_reset()
     }
 }
 
@@ -357,7 +357,7 @@ pub struct User<'app, 'open> {
 
 impl User<'_, '_> {
     pub fn decryptor(&mut self, cert: &Cert) -> Result<CardDecryptor, Error> {
-        CardDecryptor::new(self.oc.card_client, cert)
+        CardDecryptor::new(self.oc.card_tx, cert)
     }
 }
 
@@ -375,14 +375,14 @@ impl Sign<'_, '_> {
         // FIXME: depending on the setting in "PW1 Status byte", only one
         // signature can be made after verification for signing
 
-        CardSigner::new(self.oc.card_client, cert)
+        CardSigner::new(self.oc.card_tx, cert)
     }
 
     pub fn signer_from_pubkey(&mut self, pubkey: PublicKey) -> CardSigner {
         // FIXME: depending on the setting in "PW1 Status byte", only one
         // signature can be made after verification for signing
 
-        CardSigner::with_pubkey(self.oc.card_client, pubkey)
+        CardSigner::with_pubkey(self.oc.card_tx, pubkey)
     }
 }
 
@@ -408,7 +408,7 @@ impl Admin<'_, '_> {
             return Err(anyhow!("Invalid char in name").into());
         };
 
-        self.oc.card_client.set_name(name.as_bytes())
+        self.oc.card_tx.set_name(name.as_bytes())
     }
 
     pub fn set_lang(&mut self, lang: &[Lang]) -> Result<Response, Error> {
@@ -416,11 +416,11 @@ impl Admin<'_, '_> {
             return Err(anyhow!("lang too long").into());
         }
 
-        self.oc.card_client.set_lang(lang)
+        self.oc.card_tx.set_lang(lang)
     }
 
     pub fn set_sex(&mut self, sex: Sex) -> Result<Response, Error> {
-        self.oc.card_client.set_sex(sex)
+        self.oc.card_tx.set_sex(sex)
     }
 
     pub fn set_url(&mut self, url: &str) -> Result<Response, Error> {
@@ -438,7 +438,7 @@ impl Admin<'_, '_> {
             // or if it's within the acceptable length:
             // send the url update to the card.
 
-            self.oc.card_client.set_url(url.as_bytes())
+            self.oc.card_tx.set_url(url.as_bytes())
         } else {
             Err(anyhow!("URL too long").into())
         }
@@ -448,13 +448,11 @@ impl Admin<'_, '_> {
         &mut self,
         pin: &str,
     ) -> Result<Response, Error> {
-        self.oc.card_client.set_resetting_code(pin.into())
+        self.oc.card_tx.set_resetting_code(pin.into())
     }
 
     pub fn reset_user_pin(&mut self, new: &str) -> Result<Response, Error> {
-        self.oc
-            .card_client
-            .reset_retry_counter_pw1(new.into(), None)
+        self.oc.card_tx.reset_retry_counter_pw1(new.into(), None)
     }
 
     /// Upload a ValidErasedKeyAmalgamation to the card as a specific KeyType.
@@ -467,7 +465,7 @@ impl Admin<'_, '_> {
         password: Option<String>,
     ) -> Result<(), Error> {
         let key = vka_as_uploadable_key(vka, password);
-        self.oc.card_client.key_import(key, key_type)
+        self.oc.card_tx.key_import(key, key_type)
     }
 
     pub fn generate_key_simple(
@@ -476,12 +474,12 @@ impl Admin<'_, '_> {
         algo: Option<AlgoSimple>,
     ) -> Result<(PublicKeyMaterial, KeyGenerationTime), Error> {
         match algo {
-            Some(algo) => self.oc.card_client.generate_key_simple(
+            Some(algo) => self.oc.card_tx.generate_key_simple(
                 public_to_fingerprint,
                 key_type,
                 algo,
             ),
-            None => self.oc.card_client.generate_key(
+            None => self.oc.card_tx.generate_key(
                 public_to_fingerprint,
                 key_type,
                 None,
diff --git a/openpgp-card-sequoia/src/decryptor.rs b/openpgp-card-sequoia/src/decryptor.rs
index 54ef097..ab49fbd 100644
--- a/openpgp-card-sequoia/src/decryptor.rs
+++ b/openpgp-card-sequoia/src/decryptor.rs
@@ -15,14 +15,14 @@ use openpgp::Cert;
 use sequoia_openpgp as openpgp;
 
 use openpgp_card::crypto_data::Cryptogram;
-use openpgp_card::{CardClient, Error};
+use openpgp_card::{CardTransaction, Error};
 
 use crate::sq_util;
 use crate::PublicKey;
 
 pub struct CardDecryptor<'a> {
     /// The OpenPGP card (authenticated to allow decryption operations)
-    card_client: &'a mut dyn CardClient,
+    card_tx: &'a mut dyn CardTransaction,
 
     /// The matching public key for the card's decryption key
     public: PublicKey,
@@ -34,11 +34,11 @@ impl<'a> CardDecryptor<'a> {
     /// An Error is returned if no match between the card's decryption
     /// key and a (sub)key of `cert` can be made.
     pub fn new(
-        card_client: &'a mut dyn CardClient,
+        card_tx: &'a mut dyn CardTransaction,
         cert: &Cert,
     ) -> Result<CardDecryptor<'a>, Error> {
         // Get the fingerprint for the decryption key from the card.
-        let ard = card_client.application_related_data()?;
+        let ard = card_tx.application_related_data()?;
         let fps = ard.fingerprints()?;
         let fp = fps.decryption();
 
@@ -48,10 +48,7 @@ impl<'a> CardDecryptor<'a> {
 
             if let Some(eka) = sq_util::get_subkey_by_fingerprint(cert, &fp)? {
                 let public = eka.key().clone();
-                Ok(Self {
-                    card_client,
-                    public,
-                })
+                Ok(Self { card_tx, public })
             } else {
                 Err(Error::InternalError(anyhow!(
                     "Failed to find (sub)key {} in cert",
@@ -85,7 +82,7 @@ impl<'a> crypto::Decryptor for CardDecryptor<'a> {
         match (ciphertext, self.public.mpis()) {
             (mpi::Ciphertext::RSA { c: ct }, mpi::PublicKey::RSA { .. }) => {
                 let dm = Cryptogram::RSA(ct.value());
-                let dec = self.card_client.decipher(dm)?;
+                let dec = self.card_tx.decipher(dm)?;
 
                 let sk = openpgp::crypto::SessionKey::from(&dec[..]);
                 Ok(sk)
@@ -109,7 +106,7 @@ impl<'a> crypto::Decryptor for CardDecryptor<'a> {
                 };
 
                 // Decryption operation on the card
-                let mut dec = self.card_client.decipher(dm)?;
+                let mut dec = self.card_tx.decipher(dm)?;
 
                 // Specifically handle return value format like Gnuk's
                 // (Gnuk returns a leading '0x04' byte and
diff --git a/openpgp-card-sequoia/src/signer.rs b/openpgp-card-sequoia/src/signer.rs
index 2dca650..3e9e55f 100644
--- a/openpgp-card-sequoia/src/signer.rs
+++ b/openpgp-card-sequoia/src/signer.rs
@@ -11,14 +11,14 @@ use openpgp::types::{Curve, PublicKeyAlgorithm};
 use sequoia_openpgp as openpgp;
 
 use openpgp_card::crypto_data::Hash;
-use openpgp_card::{CardClient, Error};
+use openpgp_card::{CardTransaction, Error};
 
 use crate::sq_util;
 use crate::PublicKey;
 
 pub struct CardSigner<'a> {
     /// The OpenPGP card (authenticated to allow signing operations)
-    card_client: &'a mut (dyn CardClient + Send + Sync),
+    card_tx: &'a mut (dyn CardTransaction + Send + Sync),
 
     /// The matching public key for the card's signing key
     public: PublicKey,
@@ -30,11 +30,11 @@ impl<'a> CardSigner<'a> {
     /// An Error is returned if no match between the card's signing
     /// key and a (sub)key of `cert` can be made.
     pub fn new(
-        card_client: &'a mut (dyn CardClient + Send + Sync),
+        card_tx: &'a mut (dyn CardTransaction + Send + Sync),
         cert: &openpgp::Cert,
     ) -> Result<CardSigner<'a>, Error> {
         // Get the fingerprint for the signing key from the card.
-        let ard = card_client.application_related_data()?;
+        let ard = card_tx.application_related_data()?;
         let fps = ard.fingerprints()?;
         let fp = fps.signature();
 
@@ -44,7 +44,7 @@ impl<'a> CardSigner<'a> {
 
             if let Some(eka) = sq_util::get_subkey_by_fingerprint(cert, &fp)? {
                 let key = eka.key().clone();
-                Ok(Self::with_pubkey(card_client, key))
+                Ok(Self::with_pubkey(card_tx, key))
             } else {
                 Err(Error::InternalError(anyhow!(
                     "Failed to find (sub)key {} in cert",
@@ -59,13 +59,10 @@ impl<'a> CardSigner<'a> {
     }
 
     pub(crate) fn with_pubkey(
-        card_client: &'a mut (dyn CardClient + Send + Sync),
+        card_tx: &'a mut (dyn CardTransaction + Send + Sync),
         public: PublicKey,
     ) -> CardSigner<'a> {
-        CardSigner {
-            card_client,
-            public,
-        }
+        CardSigner { card_tx, public }
     }
 }
 
@@ -117,7 +114,7 @@ impl<'a> crypto::Signer for CardSigner<'a> {
                     }
                 };
 
-                let sig = self.card_client.signature_for_hash(hash)?;
+                let sig = self.card_tx.signature_for_hash(hash)?;
 
                 let mpi = mpi::MPI::new(&sig[..]);
                 Ok(mpi::Signature::RSA { s: mpi })
@@ -125,7 +122,7 @@ impl<'a> crypto::Signer for CardSigner<'a> {
             (PublicKeyAlgorithm::EdDSA, mpi::PublicKey::EdDSA { .. }) => {
                 let hash = Hash::EdDSA(digest);
 
-                let sig = self.card_client.signature_for_hash(hash)?;
+                let sig = self.card_tx.signature_for_hash(hash)?;
 
                 let r = mpi::MPI::new(&sig[..32]);
                 let s = mpi::MPI::new(&sig[32..]);
@@ -143,7 +140,7 @@ impl<'a> crypto::Signer for CardSigner<'a> {
                     _ => Hash::ECDSA(digest),
                 };
 
-                let sig = self.card_client.signature_for_hash(hash)?;
+                let sig = self.card_tx.signature_for_hash(hash)?;
 
                 let len_2 = sig.len() / 2;
                 let r = mpi::MPI::new(&sig[..len_2]);
diff --git a/openpgp-card-sequoia/src/util.rs b/openpgp-card-sequoia/src/util.rs
index 3623512..d6fa603 100644
--- a/openpgp-card-sequoia/src/util.rs
+++ b/openpgp-card-sequoia/src/util.rs
@@ -27,7 +27,7 @@ use sequoia_openpgp as openpgp;
 use openpgp_card::algorithm::{Algo, Curve};
 use openpgp_card::card_do::{Fingerprint, KeyGenerationTime};
 use openpgp_card::crypto_data::{CardUploadableKey, PublicKeyMaterial};
-use openpgp_card::{CardClient, Error, KeyType};
+use openpgp_card::{CardTransaction, Error, KeyType};
 
 use crate::card::Open;
 use crate::privkey::SequoiaKey;
@@ -294,13 +294,13 @@ pub fn vka_as_uploadable_key(
 
 /// FIXME: this fn is used in card_functionality, but should be removed
 pub fn sign(
-    card_client: &mut (dyn CardClient + Send + Sync),
+    card_tx: &mut (dyn CardTransaction + Send + Sync),
     cert: &Cert,
     input: &mut dyn io::Read,
 ) -> Result<String> {
     let mut armorer = armor::Writer::new(vec![], armor::Kind::Signature)?;
     {
-        let s = signer::CardSigner::new(card_client, cert)?;
+        let s = signer::CardSigner::new(card_tx, cert)?;
 
         let message = Message::new(&mut armorer);
         let mut message = Signer::new(message, s).detached().build()?;
@@ -318,7 +318,7 @@ pub fn sign(
 
 /// FIXME: this fn is used in card_functionality, but should be removed
 pub fn decrypt(
-    card_client: &mut dyn CardClient,
+    card_tx: &mut dyn CardTransaction,
     cert: &Cert,
     msg: Vec<u8>,
     p: &dyn Policy,
@@ -327,7 +327,7 @@ pub fn decrypt(
     {
         let reader = io::BufReader::new(&msg[..]);
 
-        let d = decryptor::CardDecryptor::new(card_client, cert)?;
+        let d = decryptor::CardDecryptor::new(card_tx, cert)?;
 
         let db = DecryptorBuilder::from_reader(reader)?;
         let mut decryptor = db.with_policy(p, None, d)?;
diff --git a/openpgp-card/src/apdu.rs b/openpgp-card/src/apdu.rs
index d4a9cda..c9a3b37 100644
--- a/openpgp-card/src/apdu.rs
+++ b/openpgp-card/src/apdu.rs
@@ -13,7 +13,7 @@ use std::convert::TryFrom;
 
 use crate::apdu::command::Expect;
 use crate::apdu::{command::Command, response::RawResponse};
-use crate::{CardClient, Error, StatusBytes};
+use crate::{CardTransaction, Error, StatusBytes};
 
 /// "Maximum amount of bytes in a short APDU command or response" (from pcsc)
 const MAX_BUFFER_SIZE: usize = 264;
@@ -23,15 +23,15 @@ const MAX_BUFFER_SIZE: usize = 264;
 /// If the reply is truncated, this fn assembles all the parts and returns
 /// them as one aggregated Response.
 pub(crate) fn send_command<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     cmd: Command,
     expect_reply: bool,
 ) -> Result<RawResponse, Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     let mut resp = RawResponse::try_from(send_command_low_level(
-        card_client,
+        card_tx,
         cmd.clone(),
         if expect_reply {
             Expect::Some
@@ -42,7 +42,7 @@ where
 
     if let StatusBytes::UnknownStatus(0x6c, size) = resp.status() {
         resp = RawResponse::try_from(send_command_low_level(
-            card_client,
+            card_tx,
             cmd,
             Expect::Short(size),
         )?)?;
@@ -54,7 +54,7 @@ where
 
         // Get next chunk of data
         let next = RawResponse::try_from(send_command_low_level(
-            card_client,
+            card_tx,
             commands::get_response(),
             Expect::Short(bytes),
         )?)?;
@@ -85,15 +85,15 @@ where
 /// If the response is chained, this fn only returns one chunk, the caller
 /// needs to re-assemble the chained response-parts.
 fn send_command_low_level<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     cmd: Command,
     expect_response: Expect,
 ) -> Result<Vec<u8>, Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     let (ext_support, chaining_support, mut max_cmd_bytes, max_rsp_bytes) =
-        if let Some(caps) = card_client.card_caps() {
+        if let Some(caps) = card_tx.card_caps() {
             log::debug!("found card caps data!");
 
             (
@@ -109,13 +109,13 @@ where
             (false, false, 255, 255)
         };
 
-    // If the CardClient implementation has an inherent limit for the cmd
+    // If the CardTransaction implementation has an inherent limit for the cmd
     // size, take that limit into account.
-    // (E.g. when using scdaemon as a CardClient backend, there is a
+    // (E.g. when using scdaemon as a CardTransaction backend, there is a
     // limitation to 1000 bytes length for Assuan commands, which
     // translates to maximum command length of a bit under 500 bytes)
-    if let Some(max_cardclient_cmd_bytes) = card_client.max_cmd_len() {
-        max_cmd_bytes = usize::min(max_cmd_bytes, max_cardclient_cmd_bytes);
+    if let Some(max_card_cmd_bytes) = card_tx.max_cmd_len() {
+        max_cmd_bytes = usize::min(max_cmd_bytes, max_card_cmd_bytes);
     }
 
     log::debug!(
@@ -167,7 +167,7 @@ where
 
             log::debug!(" -> chained APDU command: {:x?}", &serialized);
 
-            let resp = card_client.transmit(&serialized, buf_size)?;
+            let resp = card_tx.transmit(&serialized, buf_size)?;
 
             log::debug!(" <- APDU response: {:x?}", &resp);
 
@@ -210,7 +210,7 @@ where
 
         log::debug!(" -> APDU command: {:x?}", &serialized);
 
-        let resp = card_client.transmit(&serialized, buf_size)?;
+        let resp = card_tx.transmit(&serialized, buf_size)?;
 
         log::debug!(" <- APDU response: {:x?}", resp);
 
diff --git a/openpgp-card/src/keys.rs b/openpgp-card/src/keys.rs
index 366be75..160eaaa 100644
--- a/openpgp-card/src/keys.rs
+++ b/openpgp-card/src/keys.rs
@@ -17,7 +17,7 @@ use crate::crypto_data::{
 };
 use crate::tlv::{length::tlv_encode_length, value::Value, Tlv};
 use crate::{apdu, KeyType};
-use crate::{CardClient, Error};
+use crate::{CardTransaction, Error};
 
 /// Generate asymmetric key pair on the card.
 ///
@@ -30,7 +30,7 @@ use crate::{CardClient, Error};
 /// `fp_from_pub` calculates the fingerprint for a public key data object and
 /// creation timestamp
 pub(crate) fn gen_key_with_metadata<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     fp_from_pub: fn(
         &PublicKeyMaterial,
         KeyGenerationTime,
@@ -40,17 +40,17 @@ pub(crate) fn gen_key_with_metadata<C: ?Sized>(
     algo: Option<&Algo>,
 ) -> Result<(PublicKeyMaterial, KeyGenerationTime), Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     // Set algo on card if it's Some
     if let Some(target_algo) = algo {
         // FIXME: caching
-        let ard = card_client.application_related_data()?; // no caching, here!
+        let ard = card_tx.application_related_data()?; // no caching, here!
         let ecap = ard.extended_capabilities()?;
 
         // Only set algo if card supports setting of algo attr
         if ecap.algo_attrs_changeable() {
-            card_client.set_algorithm_attributes(key_type, target_algo)?;
+            card_tx.set_algorithm_attributes(key_type, target_algo)?;
         } else {
             // Check if the current algo on the card is the one we want, if
             // not we return an error.
@@ -67,11 +67,11 @@ where
     }
 
     // get current (possibly updated) state of algo
-    let ard = card_client.application_related_data()?; // no caching, here!
+    let ard = card_tx.application_related_data()?; // no caching, here!
     let cur_algo = ard.algorithm_attributes(key_type)?;
 
     // generate key
-    let tlv = generate_asymmetric_key_pair(card_client, key_type)?;
+    let tlv = generate_asymmetric_key_pair(card_tx, key_type)?;
 
     // derive pubkey
     let pubkey = tlv_to_pubkey(&tlv, &cur_algo)?;
@@ -89,11 +89,11 @@ where
 
     let ts = ts.into();
 
-    card_client.set_creation_time(ts, key_type)?;
+    card_tx.set_creation_time(ts, key_type)?;
 
     // calculate/store fingerprint
     let fp = fp_from_pub(&pubkey, ts, key_type)?;
-    card_client.set_fingerprint(fp, key_type)?;
+    card_tx.set_fingerprint(fp, key_type)?;
 
     Ok((pubkey, ts))
 }
@@ -130,17 +130,17 @@ fn tlv_to_pubkey(tlv: &Tlv, algo: &Algo) -> Result<PublicKeyMaterial> {
 /// This runs the low level key generation primitive on the card.
 /// (This does not set algorithm attributes, creation time or fingerprint)
 pub(crate) fn generate_asymmetric_key_pair<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     key_type: KeyType,
 ) -> Result<Tlv, Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     // generate key
     let crt = control_reference_template(key_type)?;
     let gen_key_cmd = commands::gen_key(crt.serialize().to_vec());
 
-    let resp = apdu::send_command(card_client, gen_key_cmd, true)?;
+    let resp = apdu::send_command(card_tx, gen_key_cmd, true)?;
     resp.check_ok()?;
 
     let tlv = Tlv::try_from(resp.data()?)?;
@@ -155,21 +155,21 @@ where
 ///
 /// (See 7.2.14 GENERATE ASYMMETRIC KEY PAIR)
 pub(crate) fn public_key<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     key_type: KeyType,
 ) -> Result<PublicKeyMaterial, Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     // get current algo
-    let ard = card_client.application_related_data()?; // FIXME: caching
+    let ard = card_tx.application_related_data()?; // FIXME: caching
     let algo = ard.algorithm_attributes(key_type)?;
 
     // get public key
     let crt = control_reference_template(key_type)?;
     let get_pub_key_cmd = commands::get_pub_key(crt.serialize().to_vec());
 
-    let resp = apdu::send_command(card_client, get_pub_key_cmd, true)?;
+    let resp = apdu::send_command(card_tx, get_pub_key_cmd, true)?;
     resp.check_ok()?;
 
     let tlv = Tlv::try_from(resp.data()?)?;
@@ -184,16 +184,16 @@ where
 /// caused by checks before attempting to upload the key to the card, or by
 /// an error that the card reports during an attempt to upload the key).
 pub(crate) fn key_import<C: ?Sized>(
-    card_client: &mut C,
+    card_tx: &mut C,
     key: Box<dyn CardUploadableKey>,
     key_type: KeyType,
     algo_info: Option<AlgoInfo>,
 ) -> Result<(), Error>
 where
-    C: CardClient,
+    C: CardTransaction,
 {
     // FIXME: caching?
-    let ard = card_client.application_related_data()?;
+    let ard = card_tx.application_related_data()?;
 
     let (algo, key_cmd) = match key.private_key()? {
         PrivateKeyMaterial::R(rsa_key) => {
@@ -229,12 +229,12 @@ where
 
     // Only set algo attrs if "Extended Capabilities" lists the feature
     if ard.extended_capabilities()?.algo_attrs_changeable() {
-        card_client.set_algorithm_attributes(key_type, &algo)?;
+        card_tx.set_algorithm_attributes(key_type, &algo)?;
     }
 
-    apdu::send_command(card_client, key_cmd, false)?.check_ok()?;
-    card_client.set_fingerprint(fp, key_type)?;
-    card_client.set_creation_time(key.timestamp(), key_type)?;
+    apdu::send_command(card_tx, key_cmd, false)?.check_ok()?;
+    card_tx.set_fingerprint(fp, key_type)?;
+    card_tx.set_creation_time(key.timestamp(), key_type)?;
 
     Ok(())
 }
diff --git a/openpgp-card/src/lib.rs b/openpgp-card/src/lib.rs
index 4ed44d5..95dd0a7 100644
--- a/openpgp-card/src/lib.rs
+++ b/openpgp-card/src/lib.rs
@@ -13,8 +13,8 @@
 //! [OpenPGP implementation](https://www.openpgp.org/software/developer/).
 //!
 //! This library can't directly access cards by itself. Instead, users
-//! need to supply an implementation of the [`CardClient`] trait, to
-//! access cards.
+//! need to supply an implementation of the [`CardBackend`]
+//! / [`CardTransaction`] traits, to access cards.
 //!
 //! The companion crate
 //! [openpgp-card-pcsc](https://crates.io/crates/openpgp-card-pcsc)
@@ -55,12 +55,13 @@ use crate::tlv::tag::Tag;
 use crate::tlv::value::Value;
 use crate::tlv::Tlv;
 
-/// The CardClient trait defines communication with an OpenPGP card via a
+/// The CardTransaction trait defines communication with an OpenPGP card via a
 /// backend implementation (e.g. the pcsc backend in the crate
-/// [openpgp-card-pcsc](https://crates.io/crates/openpgp-card-pcsc)).
+/// [openpgp-card-pcsc](https://crates.io/crates/openpgp-card-pcsc)),
+/// after opening a transaction from a CardBackend.
 ///
-/// CardClient exposes low-level access to OpenPGP card functionality.
-pub trait CardClient {
+/// CardTransaction exposes low-level access to OpenPGP card functionality.
+pub trait CardTransaction {
     /// Transmit the command data in `cmd` to the card.
     ///
     /// `buf_size` is a hint to the backend (the backend may ignore it)
@@ -71,12 +72,12 @@ pub trait CardClient {
         buf_size: usize,
     ) -> Result<Vec<u8>, Error>;
 
-    /// Set the card capabilities in the CardClient.
+    /// Set the card capabilities in the CardTransaction.
     ///
     /// Setting these capabilities is typically part of a bootstrapping
     /// process: the information about the card's capabilities is typically
-    /// requested from the card using the same CardClient instance, before
-    /// the card's capabilities have been initialized.
+    /// requested from the card using the same CardTransaction instance,
+    /// before the card's capabilities have been initialized.
     fn init_card_caps(&mut self, caps: CardCaps);
 
     /// Request the card's capabilities
@@ -85,7 +86,7 @@ pub trait CardClient {
     /// determine if extended length can be used)
     fn card_caps(&self) -> Option<&CardCaps>;
 
-    /// If a CardClient implementation introduces an additional,
+    /// If a CardTransaction implementation introduces an additional,
     /// backend-specific limit for maximum number of bytes per command,
     /// this fn can indicate that limit by returning `Some(max_cmd_len)`.
     fn max_cmd_len(&self) -> Option<usize> {
@@ -110,7 +111,7 @@ pub trait CardClient {
         apdu::send_command(self, select_openpgp, false)?.try_into()
     }
 
-    /// Get a CardApp based on a CardClient.
+    /// Get a CardApp based on a CardTransaction.
     ///
     /// It is expected that SELECT has already been performed on the card
     /// beforehand.
@@ -122,7 +123,7 @@ pub trait CardClient {
         let ard = self.application_related_data()?;
 
         // Determine chaining/extended length support from card
-        // metadata and cache this information in the CardClient
+        // metadata and cache this information in the CardTransaction
         // implementation (as a CardCaps)
         let mut ext_support = false;
         let mut chaining_support = false;
@@ -877,14 +878,14 @@ pub trait CardClient {
     }
 }
 
-impl<'a> Deref for dyn CardClient + Send + Sync + 'a {
-    type Target = dyn CardClient + 'a;
+impl<'a> Deref for dyn CardTransaction + Send + Sync + 'a {
+    type Target = dyn CardTransaction + 'a;
 
     fn deref(&self) -> &Self::Target {
         self
     }
 }
-impl<'a> DerefMut for dyn CardClient + Send + Sync + 'a {
+impl<'a> DerefMut for dyn CardTransaction + Send + Sync + 'a {
     fn deref_mut(&mut self) -> &mut Self::Target {
         self
     }
diff --git a/pcsc/src/lib.rs b/pcsc/src/lib.rs
index 3fcf147..db2fd1a 100644
--- a/pcsc/src/lib.rs
+++ b/pcsc/src/lib.rs
@@ -1,8 +1,9 @@
 // SPDX-FileCopyrightText: 2021-2022 Heiko Schaefer <heiko@schaefer.name>
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
-//! This crate implements a `CardClient` backend for `openpgp-card`. It uses
-//! the PCSC middleware to access the OpenPGP application on smart cards.
+//! This crate implements a `CardBackend`/`CardTransaction` backend for
+//! `openpgp-card`. It uses the PCSC middleware to access the OpenPGP
+//! application on smart cards.
 
 use anyhow::{anyhow, Result};
 use iso7816_tlv::simple::Tlv;
@@ -11,7 +12,7 @@ use std::collections::HashMap;
 use std::convert::TryInto;
 
 use openpgp_card::card_do::ApplicationRelatedData;
-use openpgp_card::{CardCaps, CardClient, Error, SmartcardError};
+use openpgp_card::{CardCaps, CardTransaction, Error, SmartcardError};
 
 const FEATURE_VERIFY_PIN_DIRECT: u8 = 0x06;
 const FEATURE_MODIFY_PIN_DIRECT: u8 = 0x07;
@@ -37,7 +38,7 @@ pub struct PcscCard {
     reader_caps: HashMap<u8, Tlv>,
 }
 
-/// An implementation of the CardClient trait that uses the PCSC lite
+/// An implementation of the CardTransaction trait that uses the PCSC lite
 /// middleware to access the OpenPGP card application on smart cards, via a
 /// PCSC "transaction".
 ///
@@ -146,8 +147,8 @@ impl<'b> TxClient<'b> {
     }
 
     /// Try to select the OpenPGP application on a card
-    pub fn select(card_client: &mut TxClient) -> Result<(), Error> {
-        if <dyn CardClient>::select(card_client).is_ok() {
+    pub fn select(card_tx: &mut TxClient) -> Result<(), Error> {
+        if <dyn CardTransaction>::select(card_tx).is_ok() {
             Ok(())
         } else {
             Err(Error::Smartcard(SmartcardError::SelectOpenPGPCardFailed))
@@ -156,9 +157,9 @@ impl<'b> TxClient<'b> {
 
     /// Get application_related_data from card
     fn application_related_data(
-        card_client: &mut TxClient,
+        card_tx: &mut TxClient,
     ) -> Result<ApplicationRelatedData, Error> {
-        <dyn CardClient>::application_related_data(card_client).map_err(|e| {
+        <dyn CardTransaction>::application_related_data(card_tx).map_err(|e| {
             Error::Smartcard(SmartcardError::Error(format!(
                 "TxClient: failed to get application_related_data {:x?}",
                 e
@@ -207,7 +208,7 @@ impl<'b> TxClient<'b> {
     }
 }
 
-impl CardClient for TxClient<'_> {
+impl CardTransaction for TxClient<'_> {
     fn transmit(
         &mut self,
         cmd: &[u8],
@@ -656,8 +657,8 @@ impl PcscCard {
             }
         }
 
-        // Initialize CardClient (set CardCaps from ARD)
-        <dyn CardClient>::initialize(&mut txc)?;
+        // Initialize CardTransaction (set CardCaps from ARD)
+        <dyn CardTransaction>::initialize(&mut txc)?;
 
         let cc = txc.card_caps().cloned();
 
diff --git a/scdc/src/lib.rs b/scdc/src/lib.rs
index 2a89dfe..8a883bd 100644
--- a/scdc/src/lib.rs
+++ b/scdc/src/lib.rs
@@ -13,7 +13,7 @@ use sequoia_ipc::gnupg::{Agent, Context};
 use std::sync::Mutex;
 use tokio::runtime::Runtime;
 
-use openpgp_card::{CardCaps, CardClient, Error};
+use openpgp_card::{CardCaps, CardTransaction, Error};
 
 lazy_static! {
     static ref RT: Mutex<Runtime> =
@@ -48,7 +48,7 @@ const ASSUAN_LINELENGTH: usize = 1000;
 /// In particular, uploading rsa4096 keys fails via scdaemon, with such cards.
 const APDU_CMD_BYTES_MAX: usize = (ASSUAN_LINELENGTH - 25) / 2;
 
-/// An implementation of the CardClient trait that uses GnuPG's scdaemon
+/// An implementation of the CardTransaction trait that uses GnuPG's scdaemon
 /// (via GnuPG Agent) to access OpenPGP card devices.
 pub struct ScdClient {
     agent: Agent,
@@ -65,7 +65,7 @@ impl ScdClient {
         let mut card = ScdClient::new(agent, true)?;
         card.select_card(serial)?;
 
-        <dyn CardClient>::initialize(&mut card)?;
+        <dyn CardTransaction>::initialize(&mut card)?;
 
         Ok(card)
     }
@@ -79,7 +79,7 @@ impl ScdClient {
     pub fn open_yolo(agent: Option<Agent>) -> Result<Self, Error> {
         let mut card = ScdClient::new(agent, true)?;
 
-        <dyn CardClient>::initialize(&mut card)?;
+        <dyn CardTransaction>::initialize(&mut card)?;
 
         Ok(card)
     }
@@ -199,7 +199,7 @@ impl ScdClient {
     }
 }
 
-impl CardClient for ScdClient {
+impl CardTransaction for ScdClient {
     fn transmit(&mut self, cmd: &[u8], _: usize) -> Result<Vec<u8>, Error> {
         log::trace!("SCDC cmd len {}", cmd.len());
 
diff --git a/tools/src/bin/opgpcard-pin/main.rs b/tools/src/bin/opgpcard-pin/main.rs
index 8a6895b..d5075db 100644
--- a/tools/src/bin/opgpcard-pin/main.rs
+++ b/tools/src/bin/opgpcard-pin/main.rs
@@ -4,7 +4,7 @@
 use anyhow::Result;
 use structopt::StructOpt;
 
-use openpgp_card::{CardClient, Error, StatusBytes};
+use openpgp_card::{CardTransaction, Error, StatusBytes};
 use openpgp_card_pcsc::PcscCard;
 use openpgp_card_sequoia::card::Open;
 
diff --git a/tools/src/bin/opgpcard/main.rs b/tools/src/bin/opgpcard/main.rs
index 935cdca..aaa1df4 100644
--- a/tools/src/bin/opgpcard/main.rs
+++ b/tools/src/bin/opgpcard/main.rs
@@ -12,7 +12,7 @@ use sequoia_openpgp::serialize::SerializeInto;
 use sequoia_openpgp::Cert;
 
 use openpgp_card::algorithm::AlgoSimple;
-use openpgp_card::{card_do::Sex, CardClient, KeyType};
+use openpgp_card::{card_do::Sex, CardTransaction, KeyType};
 
 use openpgp_card_sequoia::card::{Admin, Open};
 use openpgp_card_sequoia::util::{make_cert, public_key_material_to_key};
@@ -156,7 +156,7 @@ fn set_identity(
     let mut card = util::open_card(ident)?;
     let mut txc = card.transaction()?;
 
-    <dyn CardClient>::set_identity(&mut txc, id)?;
+    <dyn CardTransaction>::set_identity(&mut txc, id)?;
 
     Ok(())
 }