diff --git a/Cargo.toml b/Cargo.toml
index ce7a1c2..1618660 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "ctap_hmac"
 description = "A Rust implementation of the FIDO2 CTAP protocol, including the HMAC extension"
-version = "0.4.0"
+version = "0.4.2"
 license = "Apache-2.0/MIT"
 homepage = "https://github.com/shimunn/ctap"
 repository = "https://github.com/shimunn/ctap"
diff --git a/examples/hmac.rs b/examples/hmac.rs
index ac8834e..4f55e60 100644
--- a/examples/hmac.rs
+++ b/examples/hmac.rs
@@ -2,7 +2,7 @@ extern crate ctap_hmac as ctap;
 
 use crypto::digest::Digest;
 use crypto::sha2::Sha256;
-use ctap::extensions::hmac::HmacExtension;
+use ctap::extensions::{self, FidoExtensionResponseParserExt};
 use ctap::{FidoAssertionRequestBuilder, FidoCredential, FidoCredentialRequestBuilder};
 use hex;
 use std::env::args;
@@ -16,14 +16,13 @@ fn main() -> ctap::FidoResult<()> {
     let mut devices = ctap::get_devices()?;
     let device_info = &mut devices.next().expect("No authenticator found");
     let mut device = ctap::FidoDevice::new(device_info)?;
-
-    let credential = match args().skip(1).next().map(|h| FidoCredential {
+    let credential = match args().nth(1).map(|h| FidoCredential {
         id: hex::decode(&h).expect("Invalid credential"),
         public_key: None,
     }) {
         Some(cred) => cred,
         _ => {
-            let req = FidoCredentialRequestBuilder::default()
+            let mut req = FidoCredentialRequestBuilder::default()
                 .rp_id(RP_ID)
                 .rp_name("ctap_hmac crate")
                 .user_name("example")
@@ -31,9 +30,16 @@ fn main() -> ctap::FidoResult<()> {
                 .build()
                 .unwrap();
 
+            assert!(
+                &device.supports_extension::<extensions::HmacSecret>(),
+                "Your device does not support the hmac extension"
+            );
+            let hmac = extensions::HmacSecret::new();
+            req.with_extension(&hmac)?;
+            dbg!(&req);
             println!("Authorize using your device");
-            let cred = device
-                .make_hmac_credential(&req)
+            let cred = req
+                .make_credential(&mut device)
                 .expect("Failed to request credential");
             println!("Credential: {}\nNote: You can pass this credential as first argument in order to reproduce results", hex::encode(&cred.id));
             cred
@@ -52,12 +58,15 @@ fn main() -> ctap::FidoResult<()> {
     digest.input(&message.as_bytes());
     digest.result(&mut salt);
     let credential = &&credential;
-    let request = FidoAssertionRequestBuilder::default()
+    let hmac = extensions::HmacSecret::new().for_device(&mut device, &salt, None)?;
+    let mut request = FidoAssertionRequestBuilder::default()
         .rp_id(RP_ID)
         .credential(credential)
         .build()
         .unwrap();
-    let (_cred, (hash1, _hash2)) = device.get_hmac_assertion(&request, &salt, None)?;
+    request.with_extension(&hmac)?;
+    let (_cred, auth_data) = device.get_assertion(&request)?;
+    let (hash1, _hash2) = auth_data.parse_extension_data(&hmac)?;
     println!("Hash: {}", hex::encode(&hash1));
     Ok(())
 }
diff --git a/src/cbor.rs b/src/cbor.rs
index 7cdb27a..f74f4d6 100644
--- a/src/cbor.rs
+++ b/src/cbor.rs
@@ -592,7 +592,7 @@ impl P256Key {
     }
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Clone)]
 pub struct CoseKey {
     key_type: u16,
     algorithm: i32,
diff --git a/src/crypto.rs b/src/crypto.rs
index 1fa4902..31a0d66 100644
--- a/src/crypto.rs
+++ b/src/crypto.rs
@@ -15,7 +15,7 @@ use rust_crypto::buffer::{RefReadBuffer, RefWriteBuffer};
 use rust_crypto::symmetriccipher::{Decryptor, Encryptor};
 use untrusted::Input;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct SharedSecret {
     pub public_key: CoseKey,
     pub shared_secret: [u8; 32],
diff --git a/src/extensions/cred_protect.rs b/src/extensions/cred_protect.rs
new file mode 100644
index 0000000..de39c0c
--- /dev/null
+++ b/src/extensions/cred_protect.rs
@@ -0,0 +1,57 @@
+use crate::extensions::FidoExtension;
+use crate::FidoResult;
+use crate::{FidoAssertionRequest, FidoCredentialRequest};
+use cbor_codec::value::Value;
+use num_traits::ToPrimitive;
+
+#[derive(Copy, Clone, Debug, FromPrimitive, ToPrimitive, PartialEq)]
+pub enum CredProtectLevel {
+    UvOptional = 0x01,
+    UvOptionalWithCredentialIDList = 0x02,
+    UvRequired = 0x03,
+}
+
+impl CredProtectLevel {
+    fn extension_input(self) -> Value {
+        Value::U8(self.to_u8().unwrap())
+    }
+}
+
+pub struct CredProtect(Value);
+
+impl CredProtect {
+    pub fn level(level: CredProtectLevel) -> Self {
+        Self(level.extension_input())
+    }
+
+    fn extension_name() -> &'static str {
+        "credProtect"
+    }
+
+    fn extension_input(&self) -> &Value {
+        &self.0
+    }
+}
+
+impl FidoExtension for CredProtect {
+    fn extension_name() -> &'static str {
+        CredProtect::extension_name()
+    }
+
+    fn patch_assertion_request<'a, 'b>(
+        &'b self,
+        _request: &mut FidoAssertionRequest<'a, 'b>,
+    ) -> FidoResult<()> {
+        Ok(())
+    }
+
+    fn patch_credential_request<'a>(
+        &'a self,
+        request: &mut FidoCredentialRequest<'a>,
+    ) -> FidoResult<()> {
+        request
+            .extension_data
+            .insert(CredProtect::extension_name(), self.extension_input());
+        Ok(())
+    }
+}
diff --git a/src/extensions/hmac.rs b/src/extensions/hmac.rs
index cd8d900..27da0f4 100644
--- a/src/extensions/hmac.rs
+++ b/src/extensions/hmac.rs
@@ -1,8 +1,14 @@
+use crate::cbor::AuthenticatorData;
+use crate::crypto::SharedSecret;
+use crate::extensions::{
+    FidoExtension, FidoExtensionResponseParser, FidoExtensionResponseParserExt,
+};
 use crate::{FidoAssertionRequest, FidoAssertionRequestBuilder, FidoCredentialRequest};
 use crate::{FidoCredential, FidoDevice, FidoErrorKind, FidoResult};
 use cbor_codec::value::{Bytes, Int, Key, Text, Value};
 use cbor_codec::Encoder;
 use cbor_codec::{Config, GenericDecoder};
+use failure::ResultExt;
 use rust_crypto::buffer::{RefReadBuffer, RefWriteBuffer};
 use rust_crypto::digest::Digest;
 use rust_crypto::hmac::Hmac;
@@ -11,6 +17,7 @@ use rust_crypto::sha2::Sha256;
 use std::collections::BTreeMap;
 use std::io::Cursor;
 
+//#[deprecated]
 pub trait HmacExtension {
     fn extension_name() -> &'static str {
         "hmac-secret"
@@ -85,7 +92,67 @@ pub trait HmacExtension {
 
 impl HmacExtension for FidoDevice {
     fn get_data(&mut self, salt: &[u8; 32], salt2: Option<&[u8; 32]>) -> FidoResult<Value> {
-        let shared_secret = self.shared_secret.as_ref().unwrap();
+        Ok(HmacSecret::extension_input(self, salt, salt2)?)
+    }
+
+    fn make_hmac_credential(
+        &mut self,
+        request: &FidoCredentialRequest,
+    ) -> FidoResult<FidoCredential> {
+        let mut request = request.clone();
+        request.rk = true;
+        request.extension_data.insert(
+            <Self as HmacExtension>::extension_name(),
+            <Self as HmacExtension>::extension_input(),
+        );
+        self.make_credential(&request)
+    }
+
+    fn get_hmac_assertion<'a: 'b, 'b>(
+        &mut self,
+        request: &FidoAssertionRequest<'a, 'b>,
+        salt: &[u8; 32],
+        salt2: Option<&[u8; 32]>,
+    ) -> FidoResult<(&'a FidoCredential, ([u8; 32], Option<[u8; 32]>))> {
+        while self.shared_secret.is_none() {
+            self.init_shared_secret()?;
+        }
+        let mut request = request.clone();
+        let ext = HmacSecret::new().for_device(self, salt, salt2)?;
+        request.with_extension(&ext)?;
+
+        let (cred, auth_data) = self.get_assertion(&request)?;
+
+        let cred = request
+            .credentials
+            .iter()
+            .find(|c| c.id == cred.id)
+            .unwrap();
+        Ok((cred, auth_data.parse_extension_data(&ext)?))
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum HmacSecret {
+    Assertion {
+        extension_data: Value,
+        shared_secret: SharedSecret,
+        salt2: bool,
+    },
+    Credential,
+}
+
+impl HmacSecret {
+    pub fn new() -> Self {
+        Self::Credential
+    }
+
+    fn extension_input(
+        device: &mut FidoDevice,
+        salt: &[u8; 32],
+        salt2: Option<&[u8; 32]>,
+    ) -> FidoResult<Value> {
+        let shared_secret = device.shared_secret.as_ref().unwrap();
         let mut encryptor = shared_secret.encryptor();
         let mut salt_enc = [0u8; 64];
         let mut output = RefWriteBuffer::new(&mut salt_enc);
@@ -113,7 +180,7 @@ impl HmacExtension for FidoDevice {
         let mut map = BTreeMap::new();
         map.insert(
             Key::Int(Int::from_i64(0x01)),
-            key_agreement().map_err(|_| FidoErrorKind::Io)?,
+            key_agreement().context(FidoErrorKind::Io)?,
         );
         map.insert(
             Key::Int(Int::from_i64(0x02)),
@@ -136,42 +203,67 @@ impl HmacExtension for FidoDevice {
         Ok(Value::Map(map))
     }
 
-    fn make_hmac_credential(
+    pub fn for_device(
         &mut self,
-        request: &FidoCredentialRequest,
-    ) -> FidoResult<FidoCredential> {
-        let mut request = request.clone();
-        request.rk = true;
-        request.extension_data.insert(
-            <Self as HmacExtension>::extension_name(),
-            <Self as HmacExtension>::extension_input(),
-        );
-        self.make_credential(&request)
-    }
-
-    fn get_hmac_assertion<'a: 'b, 'b>(
-        &mut self,
-        request: &FidoAssertionRequest<'a, 'b>,
+        device: &mut FidoDevice,
         salt: &[u8; 32],
         salt2: Option<&[u8; 32]>,
-    ) -> FidoResult<(&'a FidoCredential, ([u8; 32], Option<[u8; 32]>))> {
-        while self.shared_secret.is_none() {
-            self.init_shared_secret()?;
-        }
-        let ext_data: Value = self.get_data(salt, salt2)?;
-        let mut request = request.clone();
+    ) -> FidoResult<Self> {
+        Ok(Self::Assertion {
+            extension_data: Self::extension_input(device, salt, salt2)?,
+            shared_secret: device.shared_secret.as_ref().unwrap().clone(),
+            salt2: salt2.is_some(),
+        })
+    }
+}
+
+impl FidoExtension for HmacSecret {
+    fn extension_name() -> &'static str {
+        "hmac-secret"
+    }
+
+    fn patch_assertion_request<'a, 'b>(
+        &'b self,
+        request: &mut FidoAssertionRequest<'a, 'b>,
+    ) -> FidoResult<()> {
+        match self {
+            Self::Assertion { extension_data, .. } => request
+                .extension_data
+                .insert(Self::extension_name(), extension_data),
+            _ => return Err(FidoErrorKind::DeviceUnsupported.into()),
+        };
+        Ok(())
+    }
+
+    fn patch_credential_request<'a>(
+        &'a self,
+        request: &mut FidoCredentialRequest<'a>,
+    ) -> FidoResult<()> {
         request
             .extension_data
-            .insert(<Self as HmacExtension>::extension_name(), &ext_data);
+            .insert(Self::extension_name(), &Value::Bool(true));
+        Ok(())
+    }
+}
 
-        let (cred, auth_data) = self.get_assertion(&request)?;
-        let shared_secret = self.shared_secret.as_ref().unwrap();
+impl FidoExtensionResponseParser for HmacSecret {
+    type Output = ([u8; 32], Option<[u8; 32]>);
+
+    fn parse_response(&self, response: &AuthenticatorData) -> FidoResult<Self::Output> {
+        let (shared_secret, salt2) = match self {
+            Self::Assertion {
+                shared_secret,
+                salt2,
+                ..
+            } => (shared_secret, salt2),
+            _ => return Err(FidoErrorKind::DeviceUnsupported.into()),
+        };
         let mut decryptor = shared_secret.decryptor();
         let mut hmac_secret_combined = [0u8; 64];
         let _output = RefWriteBuffer::new(&mut hmac_secret_combined);
-        let hmac_secret_enc = match auth_data
+        let hmac_secret_enc = match response
             .extensions
-            .get(<Self as HmacExtension>::extension_name())
+            .get(Self::extension_name())
             .ok_or(FidoErrorKind::CborDecode)?
         {
             Value::Bytes(hmac_ciphered) => Ok(match hmac_ciphered {
@@ -196,11 +288,6 @@ impl HmacExtension for FidoDevice {
         let mut hmac_secret_1 = [0u8; 32];
         hmac_secret_0.copy_from_slice(&hmac_secret[0..32]);
         hmac_secret_1.copy_from_slice(&hmac_secret[32..]);
-        let cred = request
-            .credentials
-            .into_iter()
-            .find(|c| c.id == cred.id)
-            .unwrap();
-        Ok((cred, (hmac_secret_0, salt2.and(Some(hmac_secret_1)))))
+        Ok((hmac_secret_0, Some(hmac_secret_1).filter(|_| *salt2)))
     }
 }
diff --git a/src/extensions/mod.rs b/src/extensions/mod.rs
index 07d0006..7f6fffc 100644
--- a/src/extensions/mod.rs
+++ b/src/extensions/mod.rs
@@ -1,2 +1,36 @@
 pub mod hmac;
 pub use hmac::*;
+mod cred_protect;
+use crate::cbor::AuthenticatorData;
+use crate::{FidoAssertionRequest, FidoCredentialRequest, FidoResult};
+pub use cred_protect::*;
+
+pub trait FidoExtension {
+    fn extension_name() -> &'static str;
+    fn patch_assertion_request<'a, 'b>(
+        &'b self,
+        request: &mut FidoAssertionRequest<'a, 'b>,
+    ) -> FidoResult<()>;
+    fn patch_credential_request<'a>(
+        &'a self,
+        request: &mut FidoCredentialRequest<'a>,
+    ) -> FidoResult<()>;
+}
+
+pub trait FidoExtensionResponseParser {
+    type Output;
+    fn parse_response(&self, response: &AuthenticatorData) -> FidoResult<Self::Output>;
+}
+
+pub trait FidoExtensionResponseParserExt<Ext: FidoExtensionResponseParser> {
+    fn parse_extension_data(&self, extension: &Ext) -> FidoResult<Ext::Output>;
+}
+
+impl<Ext: FidoExtensionResponseParser> FidoExtensionResponseParserExt<Ext> for AuthenticatorData {
+    fn parse_extension_data(
+        &self,
+        extension: &Ext,
+    ) -> FidoResult<<Ext as FidoExtensionResponseParser>::Output> {
+        extension.parse_response(self)
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 61739f6..9cba98f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -74,8 +74,9 @@ pub use self::error::*;
 use self::hid_linux as hid;
 use self::packet::CtapCommand;
 pub use self::util::*;
-use crate::cbor::{AuthenticatorData, GetAssertionRequest};
+use crate::cbor::{AuthenticatorData, GetAssertionRequest, GetInfoResponse};
 use crate::packet::CtapStatus;
+use crate::extensions::FidoExtension;
 use failure::{Fail, ResultExt};
 use num_traits::FromPrimitive;
 use rand::prelude::*;
@@ -108,6 +109,7 @@ pub struct FidoDevice {
     shared_secret: Option<crypto::SharedSecret>,
     pin_token: Option<crypto::PinToken>,
     aaguid: [u8; 16],
+    info: GetInfoResponse,
 }
 
 pub struct FidoCancelHandle {
@@ -205,6 +207,10 @@ impl<'a> FidoCredentialRequest<'a> {
     pub fn make_credential(&self, device: &mut FidoDevice) -> FidoResult<FidoCredential> {
         device.make_credential(&self)
     }
+
+    pub fn with_extension<Ext: FidoExtension>(&mut self, extension: &'a Ext) -> FidoResult<()> {
+        extension.patch_credential_request(self)
+    }
 }
 
 /// Request an assertion from the authenticator for a given credential.
@@ -240,6 +246,10 @@ impl<'a, 'b> FidoAssertionRequest<'a, 'b> {
     pub fn get_assertion(&self, device: &mut FidoDevice) -> FidoResult<&'a FidoCredential> {
         device.get_assertion(self).map(|res| res.0)
     }
+
+    pub fn with_extension<Ext: FidoExtension>(&mut self, extension: &'b Ext) -> FidoResult<()> {
+        extension.patch_assertion_request(self)
+    }
 }
 
 impl<'a, 'b> FidoAssertionRequestBuilder<'a, 'b> {
@@ -267,6 +277,7 @@ impl FidoDevice {
             shared_secret: None,
             pin_token: None,
             aaguid: [0; 16],
+            info: GetInfoResponse::default(),
         };
         dev.init()?;
         Ok(dev)
@@ -301,6 +312,7 @@ impl FidoDevice {
         }
         self.needs_pin = response.options.client_pin == Some(true);
         self.aaguid = response.aaguid;
+        self.info = response;
         Ok(())
     }
 
@@ -370,6 +382,10 @@ impl FidoDevice {
             .context(FidoErrorKind::Io)?)
     }
 
+    pub fn supports_extension<Ext: FidoExtension>(&self) -> bool {
+        self.info.extensions.iter().any(|ext| ext == Ext::extension_name())
+    }
+
     pub fn make_credential(
         &mut self,
         request: &FidoCredentialRequest<'_>,