diff --git a/openpgp-card-sequoia/examples/test.rs b/openpgp-card-sequoia/examples/test.rs
index 15178ad..fcf4644 100644
--- a/openpgp-card-sequoia/examples/test.rs
+++ b/openpgp-card-sequoia/examples/test.rs
@@ -10,10 +10,10 @@ use sequoia_openpgp::policy::StandardPolicy;
 use sequoia_openpgp::Cert;
 
 use openpgp_card::card_do::Sex;
-use openpgp_card::{KeyType, OpenPgp};
+use openpgp_card::KeyType;
 use openpgp_card_pcsc::PcscBackend;
 
-use openpgp_card_sequoia::card::Open;
+use openpgp_card_sequoia::card::{Card, Open};
 use openpgp_card_sequoia::sq_util;
 
 // Filename of test key and test message to use
@@ -36,47 +36,47 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     if let Ok(test_card_ident) = test_card_ident {
         let backend = PcscBackend::open_by_ident(&test_card_ident, None)?;
-        let mut pgp = OpenPgp::new(backend);
 
-        let mut open = Open::new(pgp.transaction()?)?;
+        let mut card: Card<Open> = backend.into();
+        let mut transaction = card.transaction()?;
 
         // card metadata
 
-        let app_id = open.application_identifier()?;
+        let app_id = transaction.application_identifier()?;
         println!("{:x?}\n", app_id);
 
-        let eli = open.extended_length_information()?;
+        let eli = transaction.extended_length_information()?;
         println!("extended_length_info: {:?}\n", eli);
 
-        let hist = open.historical_bytes()?;
+        let hist = transaction.historical_bytes()?;
         println!("{:#x?}\n", hist);
 
-        let ext = open.extended_capabilities()?;
+        let ext = transaction.extended_capabilities()?;
         println!("{:#x?}\n", ext);
 
-        let pws = open.pw_status_bytes()?;
+        let pws = transaction.pw_status_bytes()?;
         println!("{:#x?}\n", pws);
 
         // cardholder
-        let ch = open.cardholder_related_data()?;
+        let ch = transaction.cardholder_related_data()?;
         println!("{:#x?}\n", ch);
 
         // crypto-ish metadata
-        let fp = open.fingerprints()?;
+        let fp = transaction.fingerprints()?;
         println!("Fingerprint {:#x?}\n", fp);
 
-        match open.algorithm_information() {
+        match transaction.algorithm_information() {
             Ok(Some(ai)) => println!("Algorithm information:\n{}", ai),
             Ok(None) => println!("No Algorithm information found"),
             Err(e) => println!("Error getting Algorithm information: {:?}", e),
         }
 
         println!("Current algorithm attributes on card:");
-        let algo = open.algorithm_attributes(KeyType::Signing)?;
+        let algo = transaction.algorithm_attributes(KeyType::Signing)?;
         println!("Sig: {}", algo);
-        let algo = open.algorithm_attributes(KeyType::Decryption)?;
+        let algo = transaction.algorithm_attributes(KeyType::Decryption)?;
         println!("Dec: {}", algo);
-        let algo = open.algorithm_attributes(KeyType::Authentication)?;
+        let algo = transaction.algorithm_attributes(KeyType::Authentication)?;
         println!("Aut: {}", algo);
 
         println!();
@@ -88,20 +88,20 @@ fn main() -> Result<(), Box<dyn Error>> {
 
         assert_eq!(app_id.ident(), test_card_ident.to_ascii_uppercase());
 
-        let check = open.check_admin_verified();
+        let check = transaction.check_admin_verified();
         println!("has admin (pw3) been verified yet?\n{:x?}\n", check);
 
         println!("factory reset\n");
-        open.factory_reset()?;
+        transaction.factory_reset()?;
 
-        open.verify_admin(b"12345678")?;
+        transaction.verify_admin(b"12345678")?;
         println!("verify for admin ok");
 
-        let check = open.check_user_verified();
+        let check = transaction.check_user_verified();
         println!("has user (pw1/82) been verified yet? {:x?}", check);
 
         // Use Admin access to card
-        let mut admin = open.admin_card().expect("just verified");
+        let mut admin = transaction.admin_card().expect("just verified");
 
         println!();
 
@@ -141,25 +141,25 @@ fn main() -> Result<(), Box<dyn Error>> {
         //  Open fresh Card for decrypt
         // -----------------------------
         let backend = PcscBackend::open_by_ident(&test_card_ident, None)?;
-        let mut pgp = OpenPgp::new(backend);
 
-        let mut open = Open::new(pgp.transaction()?)?;
+        let mut card: Card<Open> = backend.into();
+        let mut transaction = card.transaction()?;
 
         // Check that we're still using the expected card
-        let app_id = open.application_identifier()?;
+        let app_id = transaction.application_identifier()?;
         assert_eq!(app_id.ident(), test_card_ident.to_ascii_uppercase());
 
-        let check = open.check_user_verified();
+        let check = transaction.check_user_verified();
         println!("has user (pw1/82) been verified yet?\n{:x?}\n", check);
 
-        open.verify_user(b"123456")?;
+        transaction.verify_user(b"123456")?;
         println!("verify for user (pw1/82) ok");
 
-        let check = open.check_user_verified();
+        let check = transaction.check_user_verified();
         println!("has user (pw1/82) been verified yet?\n{:x?}\n", check);
 
         // Use User access to card
-        let mut user = open
+        let mut user = transaction
             .user_card()
             .expect("We just validated, this should not fail");
 
@@ -181,16 +181,16 @@ fn main() -> Result<(), Box<dyn Error>> {
         //  Open fresh Card for signing
         // -----------------------------
         let backend = PcscBackend::open_by_ident(&test_card_ident, None)?;
-        let mut pgp = OpenPgp::new(backend);
 
-        let mut open = Open::new(pgp.transaction()?)?;
+        let mut card: Card<Open> = backend.into();
+        let mut transaction = card.transaction()?;
 
         // Sign
-        open.verify_user_for_signing(b"123456")?;
+        transaction.verify_user_for_signing(b"123456")?;
         println!("verify for sign (pw1/81) ok\n");
 
         // Use Sign access to card
-        let mut sign = open.signing_card().expect("just verified");
+        let mut sign = transaction.signing_card().expect("just verified");
 
         let _cert = Cert::from_file(TEST_KEY_PATH)?;
 
@@ -213,9 +213,8 @@ fn main() -> Result<(), Box<dyn Error>> {
         println!("The following OpenPGP cards are connected to your system:");
 
         for backend in PcscBackend::cards(None)? {
-            let mut pgp = OpenPgp::new(backend);
-
-            let open = Open::new(pgp.transaction()?)?;
+            let mut card: Card<Open> = backend.into();
+            let open = card.transaction()?;
 
             println!(" {}", open.application_identifier()?.ident());
         }
diff --git a/openpgp-card-sequoia/src/card.rs b/openpgp-card-sequoia/src/card.rs
index efea4fe..7c6a9b1 100644
--- a/openpgp-card-sequoia/src/card.rs
+++ b/openpgp-card-sequoia/src/card.rs
@@ -22,39 +22,33 @@ use crate::signer::CardSigner;
 use crate::util::{public_to_fingerprint, vka_as_uploadable_key};
 use crate::PublicKey;
 
+pub trait State {}
+impl State for Open {}
+impl State for Transaction<'_> {}
+impl State for User<'_, '_> {}
+impl State for Sign<'_, '_> {}
+impl State for Admin<'_, '_> {}
+
 /// Representation of an opened OpenPGP card in its base state (i.e. no
 /// passwords have been verified, default authorization applies).
 /// No transaction has been started.
-pub struct Card {
+pub struct Open {
     pgp: OpenPgp,
 }
 
-impl Card {
-    pub fn new<B>(backend: B) -> Self
-    where
-        B: Into<Box<dyn CardBackend + Send + Sync>>,
-    {
-        let pgp = OpenPgp::new(backend.into());
-
-        Self { pgp }
-    }
-
-    pub fn transaction(&mut self) -> Result<Open, Error> {
-        let t = self.pgp.transaction()?;
-        Open::new(t)
-    }
-}
-
 /// Representation of an opened OpenPGP card in its base state (i.e. no
 /// passwords have been verified, default authorization applies).
 /// A transaction has been started.
-pub struct Open<'a> {
+pub struct Transaction<'a> {
     opt: OpenPgpTransaction<'a>,
 
     // Cache of "application related data".
     //
     // FIXME: Should be invalidated when changing data on the card!
     // (e.g. uploading keys, etc)
+    //
+    // This field should probably be an Option<> that gets invalidated when appropriate and
+    // re-fetched lazily.
     ard: ApplicationRelatedData,
 
     // verify status of pw1
@@ -67,16 +61,67 @@ pub struct Open<'a> {
     pw3: bool,
 }
 
-impl<'a> Open<'a> {
-    pub fn new(mut ca: OpenPgpTransaction<'a>) -> Result<Self, Error> {
-        let ard = ca.application_related_data()?;
+/// An OpenPGP card after successfully verifying PW1 in mode 82
+/// (verification for user operations other than signing)
+pub struct User<'app, 'open> {
+    tx: &'open mut Card<Transaction<'app>>,
+}
+
+/// An OpenPGP card after successfully verifying PW1 in mode 81
+/// (verification for signing)
+pub struct Sign<'app, 'open> {
+    tx: &'open mut Card<Transaction<'app>>,
+}
+
+/// An OpenPGP card after successful verification of PW3 ("Admin privileges")
+pub struct Admin<'app, 'open> {
+    tx: &'open mut Card<Transaction<'app>>,
+}
+
+pub struct Card<S>
+where
+    S: State,
+{
+    state: S,
+}
+
+impl<B> From<B> for Card<Open>
+where
+    B: Into<Box<dyn CardBackend + Send + Sync>>,
+{
+    fn from(backend: B) -> Self {
+        let pgp = OpenPgp::new(backend.into());
+
+        Card::<Open> {
+            state: Open { pgp },
+        }
+    }
+}
+
+impl Card<Open> {
+    pub fn transaction(&mut self) -> Result<Card<Transaction>, Error> {
+        let opt = self.state.pgp.transaction()?;
+
+        Card::<Transaction>::new(opt)
+    }
+}
+
+impl<'a> Card<Transaction<'a>> {
+    /// Do not use!
+    ///
+    /// FIXME: this interface is currently used in `card-functionality`, for testing.
+    /// It will be removed.
+    pub fn new(mut opt: OpenPgpTransaction<'a>) -> Result<Self, Error> {
+        let ard = opt.application_related_data()?;
 
         Ok(Self {
-            opt: ca,
-            ard,
-            pw1: false,
-            pw1_sign: false,
-            pw3: false,
+            state: Transaction {
+                opt,
+                ard,
+                pw1: false,
+                pw1_sign: false,
+                pw3: false,
+            },
         })
     }
 
@@ -86,38 +131,39 @@ impl<'a> Open<'a> {
     /// This is needed e.g. after importing or generating keys on a card, to
     /// see these changes reflected in `self.ard`.
     pub fn reload_ard(&mut self) -> Result<(), Error> {
-        self.ard = self.opt.application_related_data()?;
+        // FIXME: this should be implemented internally, transparent to users
+        self.state.ard = self.state.opt.application_related_data()?;
         Ok(())
     }
 
     pub fn feature_pinpad_verify(&mut self) -> bool {
-        self.opt.feature_pinpad_verify()
+        self.state.opt.feature_pinpad_verify()
     }
 
     pub fn feature_pinpad_modify(&mut self) -> bool {
-        self.opt.feature_pinpad_modify()
+        self.state.opt.feature_pinpad_modify()
     }
 
     pub fn verify_user(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.opt.verify_pw1_user(pin)?;
-        self.pw1 = true;
+        self.state.opt.verify_pw1_user(pin)?;
+        self.state.pw1 = true;
         Ok(())
     }
 
     pub fn verify_user_pinpad(&mut self, pinpad_prompt: &dyn Fn()) -> Result<(), Error> {
         pinpad_prompt();
 
-        self.opt.verify_pw1_user_pinpad()?;
-        self.pw1 = true;
+        self.state.opt.verify_pw1_user_pinpad()?;
+        self.state.pw1 = true;
         Ok(())
     }
 
     pub fn verify_user_for_signing(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.opt.verify_pw1_sign(pin)?;
+        self.state.opt.verify_pw1_sign(pin)?;
 
         // FIXME: depending on card mode, pw1_sign is only usable once
 
-        self.pw1_sign = true;
+        self.state.pw1_sign = true;
         Ok(())
     }
 
@@ -127,25 +173,25 @@ impl<'a> Open<'a> {
     ) -> Result<(), Error> {
         pinpad_prompt();
 
-        self.opt.verify_pw1_sign_pinpad()?;
+        self.state.opt.verify_pw1_sign_pinpad()?;
 
         // FIXME: depending on card mode, pw1_sign is only usable once
 
-        self.pw1_sign = true;
+        self.state.pw1_sign = true;
         Ok(())
     }
 
     pub fn verify_admin(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.opt.verify_pw3(pin)?;
-        self.pw3 = true;
+        self.state.opt.verify_pw3(pin)?;
+        self.state.pw3 = true;
         Ok(())
     }
 
     pub fn verify_admin_pinpad(&mut self, pinpad_prompt: &dyn Fn()) -> Result<(), Error> {
         pinpad_prompt();
 
-        self.opt.verify_pw3_pinpad()?;
-        self.pw3 = true;
+        self.state.opt.verify_pw3_pinpad()?;
+        self.state.pw3 = true;
         Ok(())
     }
 
@@ -153,65 +199,71 @@ impl<'a> Open<'a> {
     ///
     /// NOTE: on some cards this functionality seems broken.
     pub fn check_user_verified(&mut self) -> Result<(), Error> {
-        self.opt.check_pw1_user()
+        self.state.opt.check_pw1_user()
     }
 
     /// 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<(), Error> {
-        self.opt.check_pw3()
+        self.state.opt.check_pw3()
     }
 
     pub fn change_user_pin(&mut self, old: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.opt.change_pw1(old, new)
+        self.state.opt.change_pw1(old, new)
     }
 
     pub fn change_user_pin_pinpad(&mut self, pinpad_prompt: &dyn Fn()) -> Result<(), Error> {
         pinpad_prompt();
-        self.opt.change_pw1_pinpad()
+        self.state.opt.change_pw1_pinpad()
     }
 
     pub fn reset_user_pin(&mut self, rst: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.opt.reset_retry_counter_pw1(new, Some(rst))
+        self.state.opt.reset_retry_counter_pw1(new, Some(rst))
     }
 
     pub fn change_admin_pin(&mut self, old: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.opt.change_pw3(old, new)
+        self.state.opt.change_pw3(old, new)
     }
 
     pub fn change_admin_pin_pinpad(&mut self, pinpad_prompt: &dyn Fn()) -> Result<(), Error> {
         pinpad_prompt();
-        self.opt.change_pw3_pinpad()
+        self.state.opt.change_pw3_pinpad()
     }
 
     /// Get a view of the card authenticated for "User" commands.
-    pub fn user_card<'b>(&'b mut self) -> Option<User<'a, 'b>> {
-        Some(User { oc: self })
+    pub fn user_card<'b>(&'b mut self) -> Option<Card<User<'a, 'b>>> {
+        Some(Card::<User> {
+            state: User { tx: self },
+        })
     }
 
     /// Get a view of the card authenticated for Signing.
-    pub fn signing_card<'b>(&'b mut self) -> Option<Sign<'a, 'b>> {
-        Some(Sign { oc: self })
+    pub fn signing_card<'b>(&'b mut self) -> Option<Card<Sign<'a, 'b>>> {
+        Some(Card::<Sign> {
+            state: Sign { tx: self },
+        })
     }
 
     /// Get a view of the card authenticated for "Admin" commands.
-    pub fn admin_card<'b>(&'b mut self) -> Option<Admin<'a, 'b>> {
-        Some(Admin { oc: self })
+    pub fn admin_card<'b>(&'b mut self) -> Option<Card<Admin<'a, 'b>>> {
+        Some(Card::<Admin> {
+            state: Admin { tx: self },
+        })
     }
 
     // --- application data ---
 
     pub fn application_identifier(&self) -> Result<ApplicationIdentifier, Error> {
-        self.ard.application_id()
+        self.state.ard.application_id()
     }
 
     pub fn historical_bytes(&self) -> Result<HistoricalBytes, Error> {
-        self.ard.historical_bytes()
+        self.state.ard.historical_bytes()
     }
 
     pub fn extended_length_information(&self) -> Result<Option<ExtendedLengthInfo>, Error> {
-        self.ard.extended_length_information()
+        self.state.ard.extended_length_information()
     }
 
     #[allow(dead_code)]
@@ -225,48 +277,48 @@ impl<'a> Open<'a> {
     }
 
     pub fn extended_capabilities(&self) -> Result<ExtendedCapabilities, Error> {
-        self.ard.extended_capabilities()
+        self.state.ard.extended_capabilities()
     }
 
     pub fn algorithm_attributes(&self, key_type: KeyType) -> Result<Algo, Error> {
-        self.ard.algorithm_attributes(key_type)
+        self.state.ard.algorithm_attributes(key_type)
     }
 
     /// PW status Bytes
     pub fn pw_status_bytes(&self) -> Result<PWStatusBytes, Error> {
-        self.ard.pw_status_bytes()
+        self.state.ard.pw_status_bytes()
     }
 
     pub fn fingerprints(&self) -> Result<KeySet<Fingerprint>, Error> {
-        self.ard.fingerprints()
+        self.state.ard.fingerprints()
     }
 
     pub fn ca_fingerprints(&self) -> Result<[Option<Fingerprint>; 3], Error> {
-        self.ard.ca_fingerprints()
+        self.state.ard.ca_fingerprints()
     }
 
     pub fn key_generation_times(&self) -> Result<KeySet<KeyGenerationTime>, Error> {
-        self.ard.key_generation_times()
+        self.state.ard.key_generation_times()
     }
 
     pub fn key_information(&self) -> Result<Option<KeyInformation>, Error> {
-        self.ard.key_information()
+        self.state.ard.key_information()
     }
 
     pub fn uif_signing(&self) -> Result<Option<UIF>, Error> {
-        self.ard.uif_pso_cds()
+        self.state.ard.uif_pso_cds()
     }
 
     pub fn uif_decryption(&self) -> Result<Option<UIF>, Error> {
-        self.ard.uif_pso_dec()
+        self.state.ard.uif_pso_dec()
     }
 
     pub fn uif_authentication(&self) -> Result<Option<UIF>, Error> {
-        self.ard.uif_pso_aut()
+        self.state.ard.uif_pso_aut()
     }
 
     pub fn uif_attestation(&self) -> Result<Option<UIF>, Error> {
-        self.ard.uif_attestation()
+        self.state.ard.uif_attestation()
     }
 
     // --- optional private DOs (0101 - 0104) ---
@@ -276,17 +328,17 @@ impl<'a> Open<'a> {
     // --- URL (5f50) ---
 
     pub fn url(&mut self) -> Result<String, Error> {
-        Ok(String::from_utf8_lossy(&self.opt.url()?).to_string())
+        Ok(String::from_utf8_lossy(&self.state.opt.url()?).to_string())
     }
 
     // --- cardholder related data (65) ---
     pub fn cardholder_related_data(&mut self) -> Result<CardholderRelatedData, Error> {
-        self.opt.cardholder_related_data()
+        self.state.opt.cardholder_related_data()
     }
 
     /// Get cardholder name as a String (this also normalizes the "<" and "<<" filler chars)
     pub fn cardholder_name(&mut self) -> Result<String, Error> {
-        let crd = self.opt.cardholder_related_data()?;
+        let crd = self.state.opt.cardholder_related_data()?;
         if let Some(name) = crd.name() {
             let name = String::from_utf8_lossy(name).to_string();
 
@@ -305,12 +357,12 @@ impl<'a> Open<'a> {
 
     // --- security support template (7a) ---
     pub fn security_support_template(&mut self) -> Result<SecuritySupportTemplate, Error> {
-        self.opt.security_support_template()
+        self.state.opt.security_support_template()
     }
 
     /// SELECT DATA ("select a DO in the current template").
     pub fn select_data(&mut self, num: u8, tag: &[u8], yk_workaround: bool) -> Result<(), Error> {
-        self.opt.select_data(num, tag, yk_workaround)
+        self.state.opt.select_data(num, tag, yk_workaround)
     }
 
     /// Get cardholder certificate.
@@ -318,7 +370,7 @@ impl<'a> Open<'a> {
     /// Call select_data() before calling this fn to select a particular
     /// certificate (if the card supports multiple certificates).
     pub fn cardholder_certificate(&mut self) -> Result<Vec<u8>, Error> {
-        self.opt.cardholder_certificate()
+        self.state.opt.cardholder_certificate()
     }
 
     /// "GET NEXT DATA" for the DO cardholder certificate.
@@ -326,7 +378,7 @@ impl<'a> Open<'a> {
     /// Cardholder certificate data for multiple slots can be read from the card by first calling
     /// cardholder_certificate(), followed by up to two calls to  next_cardholder_certificate().
     pub fn next_cardholder_certificate(&mut self) -> Result<Vec<u8>, Error> {
-        self.opt.next_cardholder_certificate()
+        self.state.opt.next_cardholder_certificate()
     }
 
     // DO "Algorithm Information" (0xFA)
@@ -340,7 +392,7 @@ impl<'a> Open<'a> {
             return Ok(None);
         }
 
-        self.opt.algorithm_information()
+        self.state.opt.algorithm_information()
     }
 
     /// "MANAGE SECURITY ENVIRONMENT"
@@ -350,19 +402,21 @@ impl<'a> Open<'a> {
         for_operation: KeyType,
         key_ref: KeyType,
     ) -> Result<(), Error> {
-        self.opt.manage_security_environment(for_operation, key_ref)
+        self.state
+            .opt
+            .manage_security_environment(for_operation, key_ref)
     }
 
     // ----------
 
     /// Get "Attestation Certificate (Yubico)"
     pub fn attestation_certificate(&mut self) -> Result<Vec<u8>, Error> {
-        self.opt.attestation_certificate()
+        self.state.opt.attestation_certificate()
     }
 
     /// Firmware Version, YubiKey specific (?)
     pub fn firmware_version(&mut self) -> Result<Vec<u8>, Error> {
-        self.opt.firmware_version()
+        self.state.opt.firmware_version()
     }
 
     /// Set "identity", Nitrokey Start specific (possible values: 0, 1, 2).
@@ -374,7 +428,7 @@ impl<'a> Open<'a> {
     /// Each virtual card identity behaves like a separate, independent OpenPGP card.
     pub fn set_identity(&mut self, id: u8) -> Result<(), Error> {
         // FIXME: what is in the returned data - is it ever useful?
-        let _ = self.opt.set_identity(id)?;
+        let _ = self.state.opt.set_identity(id)?;
 
         Ok(())
     }
@@ -382,36 +436,31 @@ impl<'a> Open<'a> {
     // ----------
 
     pub fn public_key(&mut self, key_type: KeyType) -> Result<PublicKeyMaterial, Error> {
-        self.opt.public_key(key_type)
+        self.state.opt.public_key(key_type)
     }
 
     // ----------
 
     /// Delete all state on this OpenPGP card
     pub fn factory_reset(&mut self) -> Result<(), Error> {
-        self.opt.factory_reset()
+        self.state.opt.factory_reset()
     }
 }
 
-/// An OpenPGP card after successfully verifying PW1 in mode 82
-/// (verification for user operations other than signing)
-pub struct User<'app, 'open> {
-    oc: &'open mut Open<'app>,
-}
+impl<'app, 'open> Card<User<'app, 'open>> {
+    /// Helper fn to easily access underlying openpgp_card object
+    fn card(&mut self) -> &mut OpenPgpTransaction<'app> {
+        &mut self.state.tx.state.opt
+    }
 
-impl<'app, 'open> User<'app, 'open> {
     pub fn decryptor(
         &mut self,
         touch_prompt: &'open (dyn Fn() + Send + Sync),
     ) -> Result<CardDecryptor<'_, 'app>, Error> {
-        let pk = crate::util::key_slot(self.oc, KeyType::Decryption)?
+        let pk = crate::util::key_slot(self.state.tx, KeyType::Decryption)?
             .expect("Couldn't get decryption pubkey from card");
 
-        Ok(CardDecryptor::with_pubkey(
-            &mut self.oc.opt,
-            pk,
-            touch_prompt,
-        ))
+        Ok(CardDecryptor::with_pubkey(self.card(), pk, touch_prompt))
     }
 
     pub fn decryptor_from_public(
@@ -419,18 +468,18 @@ impl<'app, 'open> User<'app, 'open> {
         pubkey: PublicKey,
         touch_prompt: &'open (dyn Fn() + Send + Sync),
     ) -> CardDecryptor<'_, 'app> {
-        CardDecryptor::with_pubkey(&mut self.oc.opt, pubkey, touch_prompt)
+        CardDecryptor::with_pubkey(self.card(), pubkey, touch_prompt)
     }
 
     pub fn authenticator(
         &mut self,
         touch_prompt: &'open (dyn Fn() + Send + Sync),
     ) -> Result<CardSigner<'_, 'app>, Error> {
-        let pk = crate::util::key_slot(self.oc, KeyType::Authentication)?
+        let pk = crate::util::key_slot(self.state.tx, KeyType::Authentication)?
             .expect("Couldn't get authentication pubkey from card");
 
         Ok(CardSigner::with_pubkey_for_auth(
-            &mut self.oc.opt,
+            self.card(),
             pk,
             touch_prompt,
         ))
@@ -440,17 +489,16 @@ impl<'app, 'open> User<'app, 'open> {
         pubkey: PublicKey,
         touch_prompt: &'open (dyn Fn() + Send + Sync),
     ) -> CardSigner<'_, 'app> {
-        CardSigner::with_pubkey_for_auth(&mut self.oc.opt, pubkey, touch_prompt)
+        CardSigner::with_pubkey_for_auth(self.card(), pubkey, touch_prompt)
     }
 }
 
-/// An OpenPGP card after successfully verifying PW1 in mode 81
-/// (verification for signing)
-pub struct Sign<'app, 'open> {
-    oc: &'open mut Open<'app>,
-}
+impl<'app, 'open> Card<Sign<'app, 'open>> {
+    /// Helper fn to easily access underlying openpgp_card object
+    fn card(&mut self) -> &mut OpenPgpTransaction<'app> {
+        &mut self.state.tx.state.opt
+    }
 
-impl<'app, 'open> Sign<'app, 'open> {
     pub fn signer(
         &mut self,
         touch_prompt: &'open (dyn Fn() + Send + Sync),
@@ -458,10 +506,10 @@ impl<'app, 'open> Sign<'app, 'open> {
         // FIXME: depending on the setting in "PW1 Status byte", only one
         // signature can be made after verification for signing
 
-        let pk = crate::util::key_slot(self.oc, KeyType::Signing)?
+        let pk = crate::util::key_slot(self.state.tx, KeyType::Signing)?
             .expect("Couldn't get signing pubkey from card");
 
-        Ok(CardSigner::with_pubkey(&mut self.oc.opt, pk, touch_prompt))
+        Ok(CardSigner::with_pubkey(self.card(), pk, touch_prompt))
     }
 
     pub fn signer_from_public(
@@ -472,7 +520,7 @@ impl<'app, 'open> Sign<'app, 'open> {
         // FIXME: depending on the setting in "PW1 Status byte", only one
         // signature can be made after verification for signing
 
-        CardSigner::with_pubkey(&mut self.oc.opt, pubkey, touch_prompt)
+        CardSigner::with_pubkey(self.card(), pubkey, touch_prompt)
     }
 
     /// Generate Attestation (Yubico)
@@ -484,28 +532,28 @@ impl<'app, 'open> Sign<'app, 'open> {
         // Touch is required if:
         // - the card supports the feature
         // - and the policy is set to a value other than 'Off'
-        if let Some(uif) = self.oc.ard.uif_attestation()? {
+        if let Some(uif) = self.state.tx.state.ard.uif_attestation()? {
             if uif.touch_policy().touch_required() {
                 (touch_prompt)();
             }
         }
 
-        self.oc.opt.generate_attestation(key_type)
+        self.card().generate_attestation(key_type)
     }
 }
 
-/// An OpenPGP card after successful verification of PW3 ("Admin privileges")
-pub struct Admin<'app, 'open> {
-    oc: &'open mut Open<'app>,
-}
+impl<'app, 'open> Card<Admin<'app, 'open>> {
+    pub fn as_open(&'_ mut self) -> &mut Card<Transaction<'app>> {
+        self.state.tx
+    }
 
-impl<'app, 'open> Admin<'app, 'open> {
-    pub fn as_open(&'_ mut self) -> &mut Open<'app> {
-        self.oc
+    /// Helper fn to easily access underlying openpgp_card object
+    fn card(&mut self) -> &mut OpenPgpTransaction<'app> {
+        &mut self.state.tx.state.opt
     }
 }
 
-impl Admin<'_, '_> {
+impl Card<Admin<'_, '_>> {
     pub fn set_name(&mut self, name: &str) -> Result<(), Error> {
         if name.len() >= 40 {
             return Err(Error::InternalError("name too long".into()));
@@ -516,7 +564,7 @@ impl Admin<'_, '_> {
             return Err(Error::InternalError("Invalid char in name".into()));
         };
 
-        self.oc.opt.set_name(name.as_bytes())
+        self.card().set_name(name.as_bytes())
     }
 
     pub fn set_lang(&mut self, lang: &[Lang]) -> Result<(), Error> {
@@ -524,11 +572,11 @@ impl Admin<'_, '_> {
             return Err(Error::InternalError("lang too long".into()));
         }
 
-        self.oc.opt.set_lang(lang)
+        self.card().set_lang(lang)
     }
 
     pub fn set_sex(&mut self, sex: Sex) -> Result<(), Error> {
-        self.oc.opt.set_sex(sex)
+        self.card().set_sex(sex)
     }
 
     pub fn set_url(&mut self, url: &str) -> Result<(), Error> {
@@ -537,7 +585,7 @@ impl Admin<'_, '_> {
         }
 
         // Check for max len
-        let ec = self.oc.extended_capabilities()?;
+        let ec = self.state.tx.extended_capabilities()?;
 
         if ec.max_len_special_do() == None || url.len() <= ec.max_len_special_do().unwrap() as usize
         {
@@ -545,7 +593,7 @@ impl Admin<'_, '_> {
             // or if it's within the acceptable length:
             // send the url update to the card.
 
-            self.oc.opt.set_url(url.as_bytes())
+            self.card().set_url(url.as_bytes())
         } else {
             Err(Error::InternalError("URL too long".into()))
         }
@@ -553,10 +601,10 @@ impl Admin<'_, '_> {
 
     pub fn set_uif(&mut self, key: KeyType, policy: TouchPolicy) -> Result<(), Error> {
         let uif = match key {
-            KeyType::Signing => self.oc.ard.uif_pso_cds()?,
-            KeyType::Decryption => self.oc.ard.uif_pso_dec()?,
-            KeyType::Authentication => self.oc.ard.uif_pso_aut()?,
-            KeyType::Attestation => self.oc.ard.uif_attestation()?,
+            KeyType::Signing => self.state.tx.state.ard.uif_pso_cds()?,
+            KeyType::Decryption => self.state.tx.state.ard.uif_pso_dec()?,
+            KeyType::Authentication => self.state.tx.state.ard.uif_pso_aut()?,
+            KeyType::Attestation => self.state.tx.state.ard.uif_attestation()?,
             _ => unimplemented!(),
         };
 
@@ -564,10 +612,10 @@ impl Admin<'_, '_> {
             uif.set_touch_policy(policy);
 
             match key {
-                KeyType::Signing => self.oc.opt.set_uif_pso_cds(&uif)?,
-                KeyType::Decryption => self.oc.opt.set_uif_pso_dec(&uif)?,
-                KeyType::Authentication => self.oc.opt.set_uif_pso_aut(&uif)?,
-                KeyType::Attestation => self.oc.opt.set_uif_attestation(&uif)?,
+                KeyType::Signing => self.card().set_uif_pso_cds(&uif)?,
+                KeyType::Decryption => self.card().set_uif_pso_dec(&uif)?,
+                KeyType::Authentication => self.card().set_uif_pso_aut(&uif)?,
+                KeyType::Attestation => self.card().set_uif_attestation(&uif)?,
                 _ => unimplemented!(),
             }
         } else {
@@ -580,15 +628,15 @@ impl Admin<'_, '_> {
     }
 
     pub fn set_resetting_code(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.oc.opt.set_resetting_code(pin)
+        self.card().set_resetting_code(pin)
     }
 
     pub fn set_pso_enc_dec_key(&mut self, key: &[u8]) -> Result<(), Error> {
-        self.oc.opt.set_pso_enc_dec_key(key)
+        self.card().set_pso_enc_dec_key(key)
     }
 
     pub fn reset_user_pin(&mut self, new: &[u8]) -> Result<(), Error> {
-        self.oc.opt.reset_retry_counter_pw1(new, None)
+        self.card().reset_retry_counter_pw1(new, None)
     }
 
     /// Upload a ValidErasedKeyAmalgamation to the card as a specific KeyType.
@@ -601,7 +649,7 @@ impl Admin<'_, '_> {
         password: Option<String>,
     ) -> Result<(), Error> {
         let key = vka_as_uploadable_key(vka, password);
-        self.oc.opt.key_import(key, key_type)
+        self.card().key_import(key, key_type)
     }
 
     /// Wrapper fn for `public_to_fingerprint` that uses SHA256/AES128 as default parameters.
@@ -628,8 +676,8 @@ impl Admin<'_, '_> {
         algo: Option<AlgoSimple>,
     ) -> Result<(PublicKeyMaterial, KeyGenerationTime), Error> {
         match algo {
-            Some(algo) => self.oc.opt.generate_key_simple(Self::ptf, key_type, algo),
-            None => self.oc.opt.generate_key(Self::ptf, key_type, None),
+            Some(algo) => self.card().generate_key_simple(Self::ptf, key_type, algo),
+            None => self.card().generate_key(Self::ptf, key_type, None),
         }
     }
 }
diff --git a/openpgp-card-sequoia/src/lib.rs b/openpgp-card-sequoia/src/lib.rs
index 2fb5f51..7a5f830 100644
--- a/openpgp-card-sequoia/src/lib.rs
+++ b/openpgp-card-sequoia/src/lib.rs
@@ -13,14 +13,14 @@
 //!
 //! ```no_run
 //! use openpgp_card_pcsc::PcscBackend;
-//! use openpgp_card_sequoia::card::Card;
+//! use openpgp_card_sequoia::card::{Card, Open};
 //!
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! for backend in PcscBackend::cards(None)? {
-//!     let mut card = Card::new(backend);
-//!     let mut open = card.transaction()?;
+//!     let mut card: Card<Open> = backend.into();
+//!     let mut transaction = card.transaction()?;
 //!     println!("Found OpenPGP card with ident '{}'",
-//!              open.application_identifier()?.ident());
+//!              transaction.application_identifier()?.ident());
 //! }
 //! # Ok(())
 //! # }
@@ -30,12 +30,12 @@
 //!
 //! ```no_run
 //! use openpgp_card_pcsc::PcscBackend;
-//! use openpgp_card_sequoia::card::Card;
+//! use openpgp_card_sequoia::card::{Card, Open};
 //!
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! let backend = PcscBackend::open_by_ident("abcd:12345678", None)?;
-//! let mut card = Card::new(backend);
-//! let mut open = card.transaction()?;
+//! let mut card: Card<Open> = backend.into();
+//! let mut transaction = card.transaction()?;
 //! # Ok(())
 //! # }
 //! ```
@@ -51,18 +51,18 @@
 //!
 //! ```no_run
 //! use openpgp_card_pcsc::PcscBackend;
-//! use openpgp_card_sequoia::card::Card;
+//! use openpgp_card_sequoia::card::{Card, Open};
 //!
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! // Open card via PCSC
 //! use sequoia_openpgp::policy::StandardPolicy;
 //! let backend = PcscBackend::open_by_ident("abcd:12345678", None)?;
-//! let mut card = Card::new(backend);
-//! let mut open = card.transaction()?;
+//! let mut card: Card<Open> = backend.into();
+//! let mut transaction = card.transaction()?;
 //!
 //! // Get authorization for user access to the card with password
-//! open.verify_user(b"123456")?;
-//! let mut user = open.user_card().expect("This should not fail");
+//! transaction.verify_user(b"123456")?;
+//! let mut user = transaction.user_card().expect("This should not fail");
 //!
 //! // Get decryptor
 //! let decryptor = user.decryptor(&|| { println!("Touch confirmation needed for decryption") });
@@ -88,17 +88,17 @@
 //!
 //! ```no_run
 //! use openpgp_card_pcsc::PcscBackend;
-//! use openpgp_card_sequoia::card::Card;
+//! use openpgp_card_sequoia::card::{Card, Open};
 //!
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! // Open card via PCSC
 //! let backend = PcscBackend::open_by_ident("abcd:12345678", None)?;
-//! let mut card = Card::new(backend);
-//! let mut open = card.transaction()?;
+//! let mut card: Card<Open> = backend.into();
+//! let mut transaction = card.transaction()?;
 //!
 //! // Get authorization for signing access to the card with password
-//! open.verify_user_for_signing(b"123456")?;
-//! let mut user = open.signing_card().expect("This should not fail");
+//! transaction.verify_user_for_signing(b"123456")?;
+//! let mut user = transaction.signing_card().expect("This should not fail");
 //!
 //! // Get signer
 //! let signer = user.signer(&|| println!("Touch confirmation needed for signing"));
@@ -114,17 +114,17 @@
 //!
 //! ```no_run
 //! use openpgp_card_pcsc::PcscBackend;
-//! use openpgp_card_sequoia::card::Card;
+//! use openpgp_card_sequoia::card::{Card, Open};
 //!
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
 //! // Open card via PCSC
 //! let backend = PcscBackend::open_by_ident("abcd:12345678", None)?;
-//! let mut card = Card::new(backend);
-//! let mut open = card.transaction()?;
+//! let mut card: Card<Open> = backend.into();
+//! let mut transaction = card.transaction()?;
 //!
 //! // Get authorization for admin access to the card with password
-//! open.verify_admin(b"12345678")?;
-//! let mut admin = open.admin_card().expect("This should not fail");
+//! transaction.verify_admin(b"12345678")?;
+//! let mut admin = transaction.admin_card().expect("This should not fail");
 //!
 //! // Set the Name and URL fields on the card
 //! admin.set_name("Bar<<Foo")?;
diff --git a/openpgp-card-sequoia/src/util.rs b/openpgp-card-sequoia/src/util.rs
index 4009285..ec58199 100644
--- a/openpgp-card-sequoia/src/util.rs
+++ b/openpgp-card-sequoia/src/util.rs
@@ -32,7 +32,7 @@ use openpgp_card::card_do::{Fingerprint, KeyGenerationTime};
 use openpgp_card::crypto_data::{CardUploadableKey, PublicKeyMaterial};
 use openpgp_card::{Error, KeyType};
 
-use crate::card::Open;
+use crate::card::{Card, Transaction};
 use crate::decryptor::CardDecryptor;
 use crate::privkey::SequoiaKey;
 use crate::signer::CardSigner;
@@ -48,7 +48,7 @@ use crate::PublicKey;
 /// FIXME: accept optional metadata for user_id(s)?
 #[allow(clippy::too_many_arguments)]
 pub fn make_cert<'app>(
-    open: &mut Open<'app>,
+    open: &mut Card<Transaction<'app>>,
     key_sig: PublicKey,
     key_dec: Option<PublicKey>,
     key_aut: Option<PublicKey>,
@@ -226,7 +226,7 @@ pub fn public_key_material_and_fp_to_key(
 }
 
 /// Get a PublicKey representation for a key slot on the card
-pub fn key_slot(open: &mut Open, kt: KeyType) -> Result<Option<PublicKey>, Error> {
+pub fn key_slot(open: &mut Card<Transaction>, kt: KeyType) -> Result<Option<PublicKey>, Error> {
     // FIXME: only read these once, if multiple subkeys are retrieved from the card
     let times = open.key_generation_times()?;
     let fps = open.fingerprints()?;