diff --git a/http-signature-normalization-actix/Cargo.toml b/http-signature-normalization-actix/Cargo.toml
index 18e8ae2..83bcffe 100644
--- a/http-signature-normalization-actix/Cargo.toml
+++ b/http-signature-normalization-actix/Cargo.toml
@@ -8,10 +8,15 @@ readme = "../README.md"
 edition = "2018"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+default = []
+digest = ["base64", "futures"]
 
 [dependencies]
 actix-web = "1.0"
+base64 = { version = "0.10", optional = true }
 http-signature-normalization = { version = "0.1.0", path = ".." }
+futures = { version = "0.1", optional = true }
 
 [dev-dependencies]
 actix = "0.8"
diff --git a/http-signature-normalization-actix/src/lib.rs b/http-signature-normalization-actix/src/lib.rs
index 820b401..a25cd3c 100644
--- a/http-signature-normalization-actix/src/lib.rs
+++ b/http-signature-normalization-actix/src/lib.rs
@@ -14,9 +14,17 @@ use std::{
     fmt::{self, Display},
 };
 
+#[cfg(feature = "digest")]
+use actix_web::{client::ClientResponse, error::PayloadError, web::Bytes};
+#[cfg(feature = "digest")]
+use futures::{Future, Stream};
+
 pub mod prelude {
     pub use crate::{verify::Unverified, Config, Sign, Verify, VerifyError};
 
+    #[cfg(feature = "digest")]
+    pub use crate::Digest;
+
     pub use actix_web::http::header::{InvalidHeaderValue, ToStrError};
 }
 
@@ -34,6 +42,13 @@ use self::{
     verify::Unverified,
 };
 
+#[cfg(feature = "digest")]
+pub trait Digest {
+    const NAME: &'static str;
+
+    fn compute(input: &[u8]) -> Vec<u8>;
+}
+
 pub trait Verify {
     fn begin_verify(&self, config: &Config) -> Result<Unverified, VerifyError>;
 }
@@ -52,6 +67,38 @@ pub trait Sign {
         E: From<ToStrError> + From<InvalidHeaderValue>,
         K: Display,
         Self: Sized;
+
+    #[cfg(feature = "digest")]
+    fn authorization_signature_with_digest<F, E, K, D, V>(
+        self,
+        config: &Config,
+        key_id: K,
+        f: F,
+        v: V,
+    ) -> Result<DigestClient<V>, E>
+    where
+        F: FnOnce(&str) -> Result<Vec<u8>, E>,
+        E: From<ToStrError> + From<InvalidHeaderValue>,
+        K: Display,
+        D: Digest,
+        V: AsRef<[u8]>,
+        Self: Sized;
+
+    #[cfg(feature = "digest")]
+    fn signature_with_digest<F, E, K, D, V>(
+        self,
+        config: &Config,
+        key_id: K,
+        f: F,
+        v: V,
+    ) -> Result<DigestClient<V>, E>
+    where
+        F: FnOnce(&str) -> Result<Vec<u8>, E>,
+        E: From<ToStrError> + From<InvalidHeaderValue>,
+        K: Display,
+        D: Digest,
+        V: AsRef<[u8]>,
+        Self: Sized;
 }
 
 #[derive(Clone, Default)]
@@ -59,6 +106,28 @@ pub struct Config {
     pub config: http_signature_normalization::Config,
 }
 
+#[cfg(feature = "digest")]
+pub struct DigestClient<V> {
+    req: ClientRequest,
+    body: V,
+}
+
+#[cfg(feature = "digest")]
+impl<V> DigestClient<V>
+where
+    V: AsRef<[u8]>,
+{
+    pub fn new(req: ClientRequest, body: V) -> Self {
+        DigestClient { req, body }
+    }
+
+    pub fn send(
+        self,
+    ) -> impl Future<Item = ClientResponse<impl Stream<Item = Bytes, Error = PayloadError>>> {
+        self.req.send_body(self.body.as_ref().to_vec())
+    }
+}
+
 #[derive(Debug)]
 pub enum VerifyError {
     Sig(http_signature_normalization::VerifyError),
@@ -158,6 +227,52 @@ impl Sign for ClientRequest {
         signed.signature_header(self.headers_mut())?;
         Ok(self)
     }
+
+    #[cfg(feature = "digest")]
+    fn authorization_signature_with_digest<F, E, K, D, V>(
+        self,
+        config: &Config,
+        key_id: K,
+        f: F,
+        v: V,
+    ) -> Result<DigestClient<V>, E>
+    where
+        F: FnOnce(&str) -> Result<Vec<u8>, E>,
+        E: From<ToStrError> + From<InvalidHeaderValue>,
+        K: Display,
+        D: Digest,
+        V: AsRef<[u8]>,
+        Self: Sized,
+    {
+        let digest = base64::encode(D::compute(v.as_ref()).as_slice());
+
+        self.set_header("Digest", format!("{}={}", D::NAME, digest))
+            .authorization_signature(config, key_id, f)
+            .map(|c| DigestClient::new(c, v))
+    }
+
+    #[cfg(feature = "digest")]
+    fn signature_with_digest<F, E, K, D, V>(
+        self,
+        config: &Config,
+        key_id: K,
+        f: F,
+        v: V,
+    ) -> Result<DigestClient<V>, E>
+    where
+        F: FnOnce(&str) -> Result<Vec<u8>, E>,
+        E: From<ToStrError> + From<InvalidHeaderValue>,
+        K: Display,
+        D: Digest,
+        V: AsRef<[u8]>,
+        Self: Sized,
+    {
+        let digest = base64::encode(D::compute(v.as_ref()).as_slice());
+
+        self.set_header("Digest", format!("{}={}", D::NAME, digest))
+            .signature(config, key_id, f)
+            .map(|c| DigestClient::new(c, v))
+    }
 }
 
 fn prepare<F, E, K>(request: &ClientRequest, config: &Config, key_id: K, f: F) -> Result<Signed, E>