diff --git a/card-functionality/src/tests.rs b/card-functionality/src/tests.rs
index 8a6ea4a..2af2ef2 100644
--- a/card-functionality/src/tests.rs
+++ b/card-functionality/src/tests.rs
@@ -193,7 +193,7 @@ pub fn test_upload_keys(
     let cert = Cert::from_file(param[0])?;
     let p = StandardPolicy::new();
 
-    let mut admin = tx.to_admin_card(b"12345678")?;
+    let mut admin = tx.to_admin_card("12345678")?;
 
     let meta = util::upload_subkeys(&mut admin, &cert, &p)
         .map_err(|e| TestError::KeyUploadError(param[0].to_string(), e))?;
@@ -246,7 +246,7 @@ pub fn test_keygen(tx: &mut Card<Transaction>, param: &[&str]) -> Result<TestOut
         key_sig,
         Some(key_dec),
         Some(key_aut),
-        Some(b"123456"),
+        Some("123456"),
         &|| {},
         &|| {},
         &[],
@@ -377,12 +377,12 @@ pub fn test_set_login_data(
 //     let d = transaction.private_use_do(1)?;
 //     println!("data 1 {d:?}");
 //
-//     transaction.verify_pw1_user(b"123456")?;
+//     transaction.verify_pw1_user("123456")?;
 //
 //     transaction.set_private_use_do(1, "Foo bar1!".as_bytes().to_vec())?;
 //     transaction.set_private_use_do(3, "Foo bar3!".as_bytes().to_vec())?;
 //
-//     transaction.verify_pw3(b"12345678")?;
+//     transaction.verify_pw3("12345678")?;
 //
 //     transaction.set_private_use_do(2, "Foo bar2!".as_bytes().to_vec())?;
 //     transaction.set_private_use_do(4, "Foo bar4!".as_bytes().to_vec())?;
@@ -513,7 +513,7 @@ pub fn test_verify(mut card: Card<Open>, _param: &[&str]) -> Result<TestOutput,
         panic!("Status should be 'SecurityStatusNotSatisfied'");
     }
 
-    transaction.verify_admin(b"12345678")?;
+    transaction.verify_admin("12345678")?;
 
     match transaction.check_admin_verified() {
         Err(Error::CardStatus(s)) => {
@@ -535,7 +535,7 @@ pub fn test_verify(mut card: Card<Open>, _param: &[&str]) -> Result<TestOutput,
     let cardholder = transaction.cardholder_related_data()?;
     assert_eq!(cardholder.name(), Some("Admin<<Hello".as_bytes()));
 
-    transaction.verify_user(b"123456")?;
+    transaction.verify_user("123456")?;
 
     match transaction.check_user_verified() {
         Err(Error::CardStatus(s)) => {
@@ -567,20 +567,20 @@ pub fn test_change_pw(mut card: Card<Open>, _param: &[&str]) -> Result<TestOutpu
     // first do admin-less pw1 on gnuk
     // (NOTE: Gnuk requires a key to be loaded before allowing pw changes!)
     println!("change pw1");
-    transaction.change_user_pin(b"123456", b"abcdef00")?;
+    transaction.change_user_pin("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
-    transaction.change_admin_pin(b"12345678", b"abcdefgh")?;
+    transaction.change_admin_pin("12345678", "abcdefgh")?;
 
     println!("change pw1");
-    transaction.change_user_pin(b"abcdef00", b"abcdef")?; // gnuk
+    transaction.change_user_pin("abcdef00", "abcdef")?; // gnuk
 
     // ca.change_pw1("123456", "abcdef")?;
 
     println!("verify bad pw1");
-    match transaction.verify_user(b"123456ab") {
+    match transaction.verify_user("123456ab") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
@@ -591,10 +591,10 @@ pub fn test_change_pw(mut card: Card<Open>, _param: &[&str]) -> Result<TestOutpu
     }
 
     println!("verify good pw1");
-    transaction.verify_user(b"abcdef")?;
+    transaction.verify_user("abcdef")?;
 
     println!("verify bad pw3");
-    match transaction.verify_admin(b"00000000") {
+    match transaction.verify_admin("00000000") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
@@ -605,13 +605,13 @@ pub fn test_change_pw(mut card: Card<Open>, _param: &[&str]) -> Result<TestOutpu
     }
 
     println!("verify good pw3");
-    transaction.verify_admin(b"abcdefgh")?;
+    transaction.verify_admin("abcdefgh")?;
 
     println!("change pw3 back to default");
-    transaction.change_admin_pin(b"abcdefgh", b"12345678")?;
+    transaction.change_admin_pin("abcdefgh", "12345678")?;
 
     println!("change pw1 back to default");
-    transaction.change_user_pin(b"abcdef", b"123456")?;
+    transaction.change_user_pin("abcdef", "123456")?;
 
     Ok(out)
 }
@@ -626,15 +626,15 @@ pub fn test_reset_retry_counter(
 
     // set pw3, then pw1 (to bring gnuk into non-admin mode)
     println!("set pw3");
-    transaction.change_admin_pin(b"12345678", b"12345678")?;
+    transaction.change_admin_pin("12345678", "12345678")?;
     println!("set pw1");
-    transaction.change_user_pin(b"123456", b"123456")?;
+    transaction.change_user_pin("123456", "123456")?;
 
     println!("break pw1");
-    let _ = transaction.verify_user(b"wrong0");
-    let _ = transaction.verify_user(b"wrong0");
-    let _ = transaction.verify_user(b"wrong0");
-    let res = transaction.verify_user(b"wrong0");
+    let _ = transaction.verify_user("wrong0");
+    let _ = transaction.verify_user("wrong0");
+    let _ = transaction.verify_user("wrong0");
+    let res = transaction.verify_user("wrong0");
 
     match res {
         Err(Error::CardStatus(StatusBytes::AuthenticationMethodBlocked)) => {
@@ -653,21 +653,21 @@ pub fn test_reset_retry_counter(
     }
 
     println!("verify pw3");
-    transaction.verify_admin(b"12345678")?;
+    transaction.verify_admin("12345678")?;
 
     println!("set resetting code");
     let mut admin = transaction.to_admin_card(None)?;
-    admin.set_resetting_code(b"abcdefgh")?;
+    admin.set_resetting_code("abcdefgh")?;
 
     println!("reset retry counter");
     // ca.reset_retry_counter_pw1("abcdef".as_bytes().to_vec(), None)?;
-    let _res = transaction.reset_user_pin(b"abcdef", b"abcdefgh");
+    let _res = transaction.reset_user_pin("abcdef", "abcdefgh");
 
     println!("verify good pw1");
-    transaction.verify_user(b"abcdef")?;
+    transaction.verify_user("abcdef")?;
 
     println!("verify bad pw1");
-    match transaction.verify_user(b"00000000") {
+    match transaction.verify_user("00000000") {
         Err(Error::CardStatus(StatusBytes::SecurityStatusNotSatisfied)) => {
             // this is expected
         }
diff --git a/openpgp-card-sequoia/examples/test.rs b/openpgp-card-sequoia/examples/test.rs
index e208e83..19b8f7f 100644
--- a/openpgp-card-sequoia/examples/test.rs
+++ b/openpgp-card-sequoia/examples/test.rs
@@ -93,7 +93,7 @@ fn main() -> Result<(), Box<dyn Error>> {
             println!("factory reset\n");
             transaction.factory_reset()?;
 
-            transaction.verify_admin(b"12345678")?;
+            transaction.verify_admin("12345678")?;
             println!("verify for admin ok");
 
             let check = transaction.check_user_verified();
@@ -152,7 +152,7 @@ fn main() -> Result<(), Box<dyn Error>> {
             let check = transaction.check_user_verified();
             println!("has user (pw1/82) been verified yet?\n{check:x?}\n");
 
-            transaction.verify_user(b"123456")?;
+            transaction.verify_user("123456")?;
             println!("verify for user (pw1/82) ok");
 
             let check = transaction.check_user_verified();
@@ -187,7 +187,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         let mut transaction = card.transaction()?;
 
         // Sign
-        transaction.verify_user_for_signing(b"123456")?;
+        transaction.verify_user_for_signing("123456")?;
         println!("verify for sign (pw1/81) ok\n");
 
         // Use Sign access to card
diff --git a/openpgp-card-sequoia/src/lib.rs b/openpgp-card-sequoia/src/lib.rs
index 57da32f..142e3bf 100644
--- a/openpgp-card-sequoia/src/lib.rs
+++ b/openpgp-card-sequoia/src/lib.rs
@@ -312,8 +312,8 @@ impl<'a> Card<Transaction<'a>> {
     }
 
     /// Verify the User PIN (for operations such as decryption)
-    pub fn verify_user(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.state.opt.verify_pw1_user(pin)?;
+    pub fn verify_user(&mut self, pin: &str) -> Result<(), Error> {
+        self.state.opt.verify_pw1_user(pin.as_bytes())?;
         self.state.pw1 = true;
         Ok(())
     }
@@ -333,8 +333,8 @@ impl<'a> Card<Transaction<'a>> {
     /// (Note that depending on the configuration of the card, this may enable
     /// performing just one signing operation, or an unlimited amount of
     /// signing operations).
-    pub fn verify_user_for_signing(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.state.opt.verify_pw1_sign(pin)?;
+    pub fn verify_user_for_signing(&mut self, pin: &str) -> Result<(), Error> {
+        self.state.opt.verify_pw1_sign(pin.as_bytes())?;
 
         // FIXME: depending on card mode, pw1_sign is only usable once
 
@@ -359,8 +359,8 @@ impl<'a> Card<Transaction<'a>> {
     }
 
     /// Verify the Admin PIN.
-    pub fn verify_admin(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.state.opt.verify_pw3(pin)?;
+    pub fn verify_admin(&mut self, pin: &str) -> Result<(), Error> {
+        self.state.opt.verify_pw3(pin.as_bytes())?;
         self.state.pw3 = true;
         Ok(())
     }
@@ -392,8 +392,8 @@ impl<'a> Card<Transaction<'a>> {
     }
 
     /// Change the User PIN, based on the old User PIN.
-    pub fn change_user_pin(&mut self, old: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.state.opt.change_pw1(old, new)
+    pub fn change_user_pin(&mut self, old: &str, new: &str) -> Result<(), Error> {
+        self.state.opt.change_pw1(old.as_bytes(), new.as_bytes())
     }
 
     /// Change the User PIN, based on the old User PIN, with a physical PIN
@@ -404,13 +404,15 @@ impl<'a> Card<Transaction<'a>> {
     }
 
     /// Change the User PIN, based on the resetting code `rst`.
-    pub fn reset_user_pin(&mut self, rst: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.state.opt.reset_retry_counter_pw1(new, Some(rst))
+    pub fn reset_user_pin(&mut self, rst: &str, new: &str) -> Result<(), Error> {
+        self.state
+            .opt
+            .reset_retry_counter_pw1(new.as_bytes(), Some(rst.as_bytes()))
     }
 
     /// Change the Admin PIN, based on the old Admin PIN.
-    pub fn change_admin_pin(&mut self, old: &[u8], new: &[u8]) -> Result<(), Error> {
-        self.state.opt.change_pw3(old, new)
+    pub fn change_admin_pin(&mut self, old: &str, new: &str) -> Result<(), Error> {
+        self.state.opt.change_pw3(old.as_bytes(), new.as_bytes())
     }
 
     /// Change the Admin PIN, based on the old Admin PIN, with a physical PIN
@@ -431,7 +433,7 @@ impl<'a> Card<Transaction<'a>> {
         let pin: OptionalPin = pin.into();
 
         if let Some(pin) = pin.0 {
-            self.verify_user(pin)?;
+            self.verify_user(String::from_utf8_lossy(pin).as_ref())?;
         }
 
         Ok(Card::<User> {
@@ -450,7 +452,7 @@ impl<'a> Card<Transaction<'a>> {
         let pin: OptionalPin = pin.into();
 
         if let Some(pin) = pin.0 {
-            self.verify_user_for_signing(pin)?;
+            self.verify_user_for_signing(String::from_utf8_lossy(pin).as_ref())?;
         }
 
         Ok(Card::<Sign> {
@@ -469,7 +471,7 @@ impl<'a> Card<Transaction<'a>> {
         let pin: OptionalPin = pin.into();
 
         if let Some(pin) = pin.0 {
-            self.verify_admin(pin)?;
+            self.verify_admin(String::from_utf8_lossy(pin).as_ref())?;
         }
 
         Ok(Card::<Admin> {
@@ -1137,16 +1139,16 @@ impl Card<Admin<'_, '_>> {
         Ok(())
     }
 
-    pub fn set_resetting_code(&mut self, pin: &[u8]) -> Result<(), Error> {
-        self.card().set_resetting_code(pin)
+    pub fn set_resetting_code(&mut self, pin: &str) -> Result<(), Error> {
+        self.card().set_resetting_code(pin.as_bytes())
     }
 
     pub fn set_pso_enc_dec_key(&mut self, key: &[u8]) -> Result<(), Error> {
         self.card().set_pso_enc_dec_key(key)
     }
 
-    pub fn reset_user_pin(&mut self, new: &[u8]) -> Result<(), Error> {
-        self.card().reset_retry_counter_pw1(new, None)
+    pub fn reset_user_pin(&mut self, new: &str) -> Result<(), Error> {
+        self.card().reset_retry_counter_pw1(new.as_bytes(), None)
     }
 
     /// Upload a ValidErasedKeyAmalgamation to the card as a specific KeyType.
diff --git a/openpgp-card-sequoia/src/util.rs b/openpgp-card-sequoia/src/util.rs
index 0288efe..91ec37b 100644
--- a/openpgp-card-sequoia/src/util.rs
+++ b/openpgp-card-sequoia/src/util.rs
@@ -42,7 +42,7 @@ pub fn make_cert(
     key_sig: PublicKey,
     key_dec: Option<PublicKey>,
     key_aut: Option<PublicKey>,
-    pw1: Option<&[u8]>,
+    pw1: Option<&str>,
     pinpad_prompt: &dyn Fn(),
     touch_prompt: &(dyn Fn() + Send + Sync),
     user_ids: &[String],