diff --git a/crates/jose/Cargo.toml b/crates/jose/Cargo.toml
index d2522dff..da672d29 100644
--- a/crates/jose/Cargo.toml
+++ b/crates/jose/Cargo.toml
@@ -22,7 +22,7 @@ schemars = "0.8.12"
 sec1 = "0.7.3"
 serde.workspace = true
 serde_json.workspace = true
-serde_with = { version = "3.3.0", features = ["base64"] }
+serde_with = "3.3.0"
 sha2 = { version = "0.10.7", features = ["oid"] }
 signature = "2.1.0"
 thiserror.workspace = true
diff --git a/crates/jose/src/base64.rs b/crates/jose/src/base64.rs
new file mode 100644
index 00000000..4bf02424
--- /dev/null
+++ b/crates/jose/src/base64.rs
@@ -0,0 +1,168 @@
+//! Transparent base64 encoding / decoding as part of (de)serialization.
+
+use std::{borrow::Cow, fmt, marker::PhantomData, str};
+
+use base64ct::Encoding;
+use serde::{
+    de::{self, Unexpected, Visitor},
+    Deserialize, Deserializer, Serialize, Serializer,
+};
+
+/// A wrapper around `Vec<u8>` that (de)serializes from / to a base64 string.
+///
+/// The generic parameter `C` represents the base64 flavor.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Base64<C = base64ct::Base64> {
+    bytes: Vec<u8>,
+    // Invariant PhantomData, Send + Sync
+    _phantom_conf: PhantomData<fn(C) -> C>,
+}
+
+pub type Base64UrlNoPad = Base64<base64ct::Base64UrlUnpadded>;
+
+impl<C: Encoding> Base64<C> {
+    /// Create a `Base64` instance from raw bytes, to be base64-encoded in
+    /// serialization.
+    #[must_use]
+    pub fn new(bytes: Vec<u8>) -> Self {
+        Self {
+            bytes,
+            _phantom_conf: PhantomData,
+        }
+    }
+
+    /// Get a reference to the raw bytes held by this `Base64` instance.
+    #[must_use]
+    pub fn as_bytes(&self) -> &[u8] {
+        self.bytes.as_ref()
+    }
+
+    /// Encode the bytes contained in this `Base64` instance to unpadded base64.
+    #[must_use]
+    pub fn encode(&self) -> String {
+        C::encode_string(self.as_bytes())
+    }
+
+    /// Get the raw bytes held by this `Base64` instance.
+    #[must_use]
+    pub fn into_inner(self) -> Vec<u8> {
+        self.bytes
+    }
+
+    /// Create a `Base64` instance containing an empty `Vec<u8>`.
+    #[must_use]
+    pub fn empty() -> Self {
+        Self::new(Vec::new())
+    }
+
+    /// Parse some base64-encoded data to create a `Base64` instance.
+    pub fn parse(encoded: &str) -> Result<Self, base64ct::Error> {
+        C::decode_vec(encoded).map(Self::new)
+    }
+}
+
+impl<C: Encoding> fmt::Debug for Base64<C> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.encode().fmt(f)
+    }
+}
+
+impl<C: Encoding> fmt::Display for Base64<C> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.encode().fmt(f)
+    }
+}
+
+impl<'de, C: Encoding> Deserialize<'de> for Base64<C> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let encoded = deserialize_cow_str(deserializer)?;
+        Self::parse(&encoded).map_err(de::Error::custom)
+    }
+}
+
+impl<C: Encoding> Serialize for Base64<C> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&self.encode())
+    }
+}
+
+/// Deserialize a `Cow<'de, str>`.
+///
+/// Different from serde's implementation of `Deserialize` for `Cow` since it
+/// borrows from the input when possible.
+pub fn deserialize_cow_str<'de, D>(deserializer: D) -> Result<Cow<'de, str>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    deserializer.deserialize_string(CowStrVisitor)
+}
+
+struct CowStrVisitor;
+
+impl<'de> Visitor<'de> for CowStrVisitor {
+    type Value = Cow<'de, str>;
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        formatter.write_str("a string")
+    }
+
+    fn visit_borrowed_str<E>(self, v: &'de str) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(Cow::Borrowed(v))
+    }
+
+    fn visit_borrowed_bytes<E>(self, v: &'de [u8]) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        match str::from_utf8(v) {
+            Ok(s) => Ok(Cow::Borrowed(s)),
+            Err(_) => Err(de::Error::invalid_value(Unexpected::Bytes(v), &self)),
+        }
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(Cow::Owned(v.to_owned()))
+    }
+
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        Ok(Cow::Owned(v))
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        match str::from_utf8(v) {
+            Ok(s) => Ok(Cow::Owned(s.to_owned())),
+            Err(_) => Err(de::Error::invalid_value(Unexpected::Bytes(v), &self)),
+        }
+    }
+
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        match String::from_utf8(v) {
+            Ok(s) => Ok(Cow::Owned(s)),
+            Err(e) => Err(de::Error::invalid_value(
+                Unexpected::Bytes(&e.into_bytes()),
+                &self,
+            )),
+        }
+    }
+}
diff --git a/crates/jose/src/jwk/mod.rs b/crates/jose/src/jwk/mod.rs
index 4e001cf2..1423cad8 100644
--- a/crates/jose/src/jwk/mod.rs
+++ b/crates/jose/src/jwk/mod.rs
@@ -20,14 +20,13 @@ use mas_iana::jose::{
 };
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use serde_with::{
-    base64::{Base64, Standard, UrlSafe},
-    formats::{Padded, Unpadded},
-    serde_as, skip_serializing_none,
-};
+use serde_with::skip_serializing_none;
 use url::Url;
 
-use crate::constraints::{Constrainable, Constraint, ConstraintSet};
+use crate::{
+    base64::{Base64, Base64UrlNoPad},
+    constraints::{Constrainable, Constraint, ConstraintSet},
+};
 
 pub(crate) mod private_parameters;
 pub(crate) mod public_parameters;
@@ -60,7 +59,6 @@ impl JwkEcCurve for k256::Secp256k1 {
     const CRV: JsonWebKeyEcEllipticCurve = JsonWebKeyEcEllipticCurve::Secp256K1;
 }
 
-#[serde_as]
 #[skip_serializing_none]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct JsonWebKey<P> {
@@ -85,18 +83,15 @@ pub struct JsonWebKey<P> {
 
     #[schemars(with = "Vec<String>")]
     #[serde(default)]
-    #[serde_as(as = "Option<Vec<Base64<Standard, Padded>>>")]
-    x5c: Option<Vec<Vec<u8>>>,
+    x5c: Option<Vec<Base64>>,
 
     #[schemars(with = "Option<String>")]
     #[serde(default)]
-    #[serde_as(as = "Option<Base64<UrlSafe, Unpadded>>")]
-    x5t: Option<Vec<u8>>,
+    x5t: Option<Base64UrlNoPad>,
 
     #[schemars(with = "Option<String>")]
     #[serde(default, rename = "x5t#S256")]
-    #[serde_as(as = "Option<Base64<UrlSafe, Unpadded>>")]
-    x5t_s256: Option<Vec<u8>>,
+    x5t_s256: Option<Base64UrlNoPad>,
 }
 
 pub type PublicJsonWebKey = JsonWebKey<self::public_parameters::JsonWebKeyPublicParameters>;
diff --git a/crates/jose/src/jwk/private_parameters.rs b/crates/jose/src/jwk/private_parameters.rs
index 29345038..aaa4635c 100644
--- a/crates/jose/src/jwk/private_parameters.rs
+++ b/crates/jose/src/jwk/private_parameters.rs
@@ -17,16 +17,11 @@ use mas_iana::jose::{
 };
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use serde_with::{
-    base64::{Base64, UrlSafe},
-    formats::Unpadded,
-    serde_as,
-};
 use thiserror::Error;
 
 use super::{public_parameters::JsonWebKeyPublicParameters, ParametersInfo};
+use crate::base64::Base64UrlNoPad;
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 #[serde(tag = "kty")]
 pub enum JsonWebKeyPrivateParameters {
@@ -114,13 +109,11 @@ impl TryFrom<JsonWebKeyPrivateParameters> for JsonWebKeyPublicParameters {
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct OctPrivateParameters {
     /// Key Value
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    k: Vec<u8>,
+    k: Base64UrlNoPad,
 }
 
 impl ParametersInfo for OctPrivateParameters {
@@ -137,48 +130,39 @@ impl ParametersInfo for OctPrivateParameters {
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct RsaPrivateParameters {
     /// Modulus
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    n: Vec<u8>,
+    n: Base64UrlNoPad,
 
     /// Exponent
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    e: Vec<u8>,
+    e: Base64UrlNoPad,
 
     /// Private Exponent
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    d: Vec<u8>,
+    d: Base64UrlNoPad,
 
     /// First Prime Factor
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    p: Vec<u8>,
+    p: Base64UrlNoPad,
 
     /// Second Prime Factor
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    q: Vec<u8>,
+    q: Base64UrlNoPad,
 
     /// First Factor CRT Exponent
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    dp: Vec<u8>,
+    dp: Base64UrlNoPad,
 
     /// Second Factor CRT Exponent
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    dq: Vec<u8>,
+    dq: Base64UrlNoPad,
 
     /// First CRT Coefficient
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    qi: Vec<u8>,
+    qi: Base64UrlNoPad,
 
     /// Other Primes Info
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -208,23 +192,19 @@ impl From<RsaPrivateParameters> for super::public_parameters::RsaPublicParameter
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 struct RsaOtherPrimeInfo {
     /// Prime Factor
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    r: Vec<u8>,
+    r: Base64UrlNoPad,
 
     /// Factor CRT Exponent
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    d: Vec<u8>,
+    d: Base64UrlNoPad,
 
     /// Factor CRT Coefficient
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    t: Vec<u8>,
+    t: Base64UrlNoPad,
 }
 
 mod rsa_impls {
@@ -244,14 +224,14 @@ mod rsa_impls {
 
         #[allow(clippy::many_single_char_names)]
         fn try_from(value: &RsaPrivateParameters) -> Result<Self, Self::Error> {
-            let n = BigUint::from_bytes_be(&value.n);
-            let e = BigUint::from_bytes_be(&value.e);
-            let d = BigUint::from_bytes_be(&value.d);
+            let n = BigUint::from_bytes_be(value.n.as_bytes());
+            let e = BigUint::from_bytes_be(value.e.as_bytes());
+            let d = BigUint::from_bytes_be(value.d.as_bytes());
 
             let primes = [&value.p, &value.q]
                 .into_iter()
                 .chain(value.oth.iter().flatten().map(|o| &o.r))
-                .map(|i| BigUint::from_bytes_be(i))
+                .map(|i| BigUint::from_bytes_be(i.as_bytes()))
                 .collect();
 
             let key = RsaPrivateKey::from_components(n, e, d, primes)?;
@@ -263,22 +243,18 @@ mod rsa_impls {
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct EcPrivateParameters {
     pub(crate) crv: JsonWebKeyEcEllipticCurve,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    x: Vec<u8>,
+    x: Base64UrlNoPad,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    y: Vec<u8>,
+    y: Base64UrlNoPad,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    d: Vec<u8>,
+    d: Base64UrlNoPad,
 }
 
 impl ParametersInfo for EcPrivateParameters {
@@ -310,6 +286,7 @@ mod ec_impls {
     };
 
     use super::{super::JwkEcCurve, EcPrivateParameters};
+    use crate::base64::Base64UrlNoPad;
 
     impl<C> TryFrom<EcPrivateParameters> for SecretKey<C>
     where
@@ -328,7 +305,7 @@ mod ec_impls {
         type Error = elliptic_curve::Error;
 
         fn try_from(value: &EcPrivateParameters) -> Result<Self, Self::Error> {
-            SecretKey::from_slice(&value.d)
+            SecretKey::from_slice(value.d.as_bytes())
         }
     }
 
@@ -357,22 +334,20 @@ mod ec_impls {
             let d = key.to_bytes();
             EcPrivateParameters {
                 crv: C::CRV,
-                x: x.to_vec(),
-                y: y.to_vec(),
-                d: d.to_vec(),
+                x: Base64UrlNoPad::new(x.to_vec()),
+                y: Base64UrlNoPad::new(y.to_vec()),
+                d: Base64UrlNoPad::new(d.to_vec()),
             }
         }
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct OkpPrivateParameters {
     crv: JsonWebKeyOkpEllipticCurve,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    x: Vec<u8>,
+    x: Base64UrlNoPad,
 }
 
 impl ParametersInfo for OkpPrivateParameters {
diff --git a/crates/jose/src/jwk/public_parameters.rs b/crates/jose/src/jwk/public_parameters.rs
index 89b1c256..3f35fb75 100644
--- a/crates/jose/src/jwk/public_parameters.rs
+++ b/crates/jose/src/jwk/public_parameters.rs
@@ -17,15 +17,10 @@ use mas_iana::jose::{
 };
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use serde_with::{
-    base64::{Base64, UrlSafe},
-    formats::Unpadded,
-    serde_as,
-};
 
 use super::ParametersInfo;
+use crate::base64::Base64UrlNoPad;
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 #[serde(tag = "kty")]
 pub enum JsonWebKeyPublicParameters {
@@ -83,16 +78,13 @@ impl ParametersInfo for JsonWebKeyPublicParameters {
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct RsaPublicParameters {
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    n: Vec<u8>,
+    n: Base64UrlNoPad,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    e: Vec<u8>,
+    e: Base64UrlNoPad,
 }
 
 impl ParametersInfo for RsaPublicParameters {
@@ -113,27 +105,24 @@ impl ParametersInfo for RsaPublicParameters {
 }
 
 impl RsaPublicParameters {
-    pub const fn new(n: Vec<u8>, e: Vec<u8>) -> Self {
+    pub const fn new(n: Base64UrlNoPad, e: Base64UrlNoPad) -> Self {
         Self { n, e }
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct EcPublicParameters {
     pub(crate) crv: JsonWebKeyEcEllipticCurve,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    x: Vec<u8>,
+    x: Base64UrlNoPad,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    y: Vec<u8>,
+    y: Base64UrlNoPad,
 }
 
 impl EcPublicParameters {
-    pub const fn new(crv: JsonWebKeyEcEllipticCurve, x: Vec<u8>, y: Vec<u8>) -> Self {
+    pub const fn new(crv: JsonWebKeyEcEllipticCurve, x: Base64UrlNoPad, y: Base64UrlNoPad) -> Self {
         Self { crv, x, y }
     }
 }
@@ -154,14 +143,12 @@ impl ParametersInfo for EcPublicParameters {
     }
 }
 
-#[serde_as]
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
 pub struct OkpPublicParameters {
     crv: JsonWebKeyOkpEllipticCurve,
 
     #[schemars(with = "String")]
-    #[serde_as(as = "Base64<UrlSafe, Unpadded>")]
-    x: Vec<u8>,
+    x: Base64UrlNoPad,
 }
 
 impl ParametersInfo for OkpPublicParameters {
@@ -175,7 +162,7 @@ impl ParametersInfo for OkpPublicParameters {
 }
 
 impl OkpPublicParameters {
-    pub const fn new(crv: JsonWebKeyOkpEllipticCurve, x: Vec<u8>) -> Self {
+    pub const fn new(crv: JsonWebKeyOkpEllipticCurve, x: Base64UrlNoPad) -> Self {
         Self { crv, x }
     }
 }
@@ -184,6 +171,7 @@ mod rsa_impls {
     use rsa::{traits::PublicKeyParts, BigUint, RsaPublicKey};
 
     use super::{JsonWebKeyPublicParameters, RsaPublicParameters};
+    use crate::base64::Base64UrlNoPad;
 
     impl From<RsaPublicKey> for JsonWebKeyPublicParameters {
         fn from(key: RsaPublicKey) -> Self {
@@ -206,8 +194,8 @@ mod rsa_impls {
     impl From<&RsaPublicKey> for RsaPublicParameters {
         fn from(key: &RsaPublicKey) -> Self {
             Self {
-                n: key.n().to_bytes_be(),
-                e: key.e().to_bytes_be(),
+                n: Base64UrlNoPad::new(key.n().to_bytes_be()),
+                e: Base64UrlNoPad::new(key.e().to_bytes_be()),
             }
         }
     }
@@ -222,8 +210,8 @@ mod rsa_impls {
     impl TryFrom<&RsaPublicParameters> for RsaPublicKey {
         type Error = rsa::errors::Error;
         fn try_from(value: &RsaPublicParameters) -> Result<Self, Self::Error> {
-            let n = BigUint::from_bytes_be(&value.n);
-            let e = BigUint::from_bytes_be(&value.e);
+            let n = BigUint::from_bytes_be(value.n.as_bytes());
+            let e = BigUint::from_bytes_be(value.e.as_bytes());
             let key = RsaPublicKey::new(n, e)?;
             Ok(key)
         }
@@ -239,6 +227,7 @@ mod ec_impls {
     };
 
     use super::{super::JwkEcCurve, EcPublicParameters, JsonWebKeyPublicParameters};
+    use crate::base64::Base64UrlNoPad;
 
     impl<C> TryFrom<&EcPublicParameters> for PublicKey<C>
     where
@@ -250,10 +239,12 @@ mod ec_impls {
         fn try_from(value: &EcPublicParameters) -> Result<Self, Self::Error> {
             let x = value
                 .x
+                .as_bytes()
                 .get(..C::FieldBytesSize::USIZE)
                 .ok_or(elliptic_curve::Error)?;
             let y = value
                 .y
+                .as_bytes()
                 .get(..C::FieldBytesSize::USIZE)
                 .ok_or(elliptic_curve::Error)?;
 
@@ -311,8 +302,8 @@ mod ec_impls {
             };
             EcPublicParameters {
                 crv: C::CRV,
-                x: x.to_vec(),
-                y: y.to_vec(),
+                x: Base64UrlNoPad::new(x.to_vec()),
+                y: Base64UrlNoPad::new(y.to_vec()),
             }
         }
     }
diff --git a/crates/jose/src/jwt/header.rs b/crates/jose/src/jwt/header.rs
index b5a0b49e..af2ad424 100644
--- a/crates/jose/src/jwt/header.rs
+++ b/crates/jose/src/jwt/header.rs
@@ -14,16 +14,11 @@
 
 use mas_iana::jose::JsonWebSignatureAlg;
 use serde::{Deserialize, Serialize};
-use serde_with::{
-    base64::{Base64, Standard, UrlSafe},
-    formats::{Padded, Unpadded},
-    serde_as, skip_serializing_none,
-};
+use serde_with::skip_serializing_none;
 use url::Url;
 
-use crate::jwk::PublicJsonWebKey;
+use crate::{base64::Base64UrlNoPad, jwk::PublicJsonWebKey, Base64};
 
-#[serde_as]
 #[skip_serializing_none]
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
 pub struct JsonWebSignatureHeader {
@@ -42,16 +37,13 @@ pub struct JsonWebSignatureHeader {
     x5u: Option<Url>,
 
     #[serde(default)]
-    #[serde_as(as = "Option<Vec<Base64<Standard, Padded>>>")]
-    x5c: Option<Vec<Vec<u8>>>,
+    x5c: Option<Vec<Base64>>,
 
     #[serde(default)]
-    #[serde_as(as = "Option<Base64<UrlSafe, Unpadded>>")]
-    x5t: Option<Vec<u8>>,
+    x5t: Option<Base64UrlNoPad>,
 
     #[serde(default, rename = "x5t#S256")]
-    #[serde_as(as = "Option<Base64<UrlSafe, Unpadded>>")]
-    x5t_s256: Option<Vec<u8>>,
+    x5t_s256: Option<Base64UrlNoPad>,
 
     #[serde(default)]
     typ: Option<String>,
diff --git a/crates/jose/src/lib.rs b/crates/jose/src/lib.rs
index 26cf1005..aa7599fa 100644
--- a/crates/jose/src/lib.rs
+++ b/crates/jose/src/lib.rs
@@ -17,8 +17,11 @@
 #![warn(clippy::pedantic)]
 #![allow(clippy::missing_errors_doc, clippy::module_name_repetitions)]
 
+mod base64;
 pub mod claims;
 pub mod constraints;
 pub mod jwa;
 pub mod jwk;
 pub mod jwt;
+
+pub use self::base64::Base64;