diff --git a/http-signature-normalization-actix/Cargo.toml b/http-signature-normalization-actix/Cargo.toml
index 60649c8..03655eb 100644
--- a/http-signature-normalization-actix/Cargo.toml
+++ b/http-signature-normalization-actix/Cargo.toml
@@ -27,6 +27,7 @@ required-features = ["sha-2"]
 [dependencies]
 actix-web = "3.0.0-alpha.1"
 actix-http = "2.0.0-alpha.2"
+async-trait = "0.1.27"
 base64 = { version = "0.11", optional = true }
 bytes = "0.5.4"
 chrono = "0.4.6"
diff --git a/http-signature-normalization-actix/src/digest/mod.rs b/http-signature-normalization-actix/src/digest/mod.rs
index 0472193..f8ad6b2 100644
--- a/http-signature-normalization-actix/src/digest/mod.rs
+++ b/http-signature-normalization-actix/src/digest/mod.rs
@@ -7,6 +7,7 @@ use actix_http::encoding::Decoder;
 use actix_web::{
     client::{ClientRequest, ClientResponse, SendRequestError},
     dev::Payload,
+    error::BlockingError,
     http::header::{InvalidHeaderValue, ToStrError},
 };
 use std::{fmt::Display, future::Future};
@@ -43,9 +44,10 @@ pub trait DigestVerify {
 /// It generates HTTP Signatures after the Digest header has been added, in order to have
 /// verification that the body has not been tampered with, or that the request can't be replayed by
 /// a malicious entity
+#[async_trait::async_trait(?Send)]
 pub trait SignExt: Sign {
     /// Set the Digest and Authorization headers on the request
-    fn authorization_signature_with_digest<F, E, K, D, V>(
+    async fn authorization_signature_with_digest<F, E, K, D, V>(
         self,
         config: &Config,
         key_id: K,
@@ -54,15 +56,20 @@ pub trait SignExt: Sign {
         f: F,
     ) -> Result<DigestClient<V>, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         D: DigestCreate,
         V: AsRef<[u8]>,
         Self: Sized;
 
     /// Set the Digest and Signature headers on the request
-    fn signature_with_digest<F, E, K, D, V>(
+    async fn signature_with_digest<F, E, K, D, V>(
         self,
         config: &Config,
         key_id: K,
@@ -71,8 +78,13 @@ pub trait SignExt: Sign {
         f: F,
     ) -> Result<DigestClient<V>, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         D: DigestCreate,
         V: AsRef<[u8]>,
diff --git a/http-signature-normalization-actix/src/digest/sign.rs b/http-signature-normalization-actix/src/digest/sign.rs
index 267849c..0d28b97 100644
--- a/http-signature-normalization-actix/src/digest/sign.rs
+++ b/http-signature-normalization-actix/src/digest/sign.rs
@@ -1,5 +1,6 @@
 use actix_web::{
     client::ClientRequest,
+    error::BlockingError,
     http::header::{InvalidHeaderValue, ToStrError},
 };
 use std::fmt::Display;
@@ -9,8 +10,9 @@ use crate::{
     Config, Sign,
 };
 
+#[async_trait::async_trait(?Send)]
 impl SignExt for ClientRequest {
-    fn authorization_signature_with_digest<F, E, K, D, V>(
+    async fn authorization_signature_with_digest<F, E, K, D, V>(
         self,
         config: &Config,
         key_id: K,
@@ -19,8 +21,13 @@ impl SignExt for ClientRequest {
         f: F,
     ) -> Result<DigestClient<V>, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         D: DigestCreate,
         V: AsRef<[u8]>,
@@ -30,10 +37,11 @@ impl SignExt for ClientRequest {
 
         self.set_header("Digest", format!("{}={}", D::NAME, digest))
             .authorization_signature(config, key_id, f)
+            .await
             .map(|c| DigestClient::new(c, v))
     }
 
-    fn signature_with_digest<F, E, K, D, V>(
+    async fn signature_with_digest<F, E, K, D, V>(
         self,
         config: &Config,
         key_id: K,
@@ -42,8 +50,13 @@ impl SignExt for ClientRequest {
         f: F,
     ) -> Result<DigestClient<V>, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         D: DigestCreate,
         V: AsRef<[u8]>,
@@ -53,6 +66,7 @@ impl SignExt for ClientRequest {
 
         self.set_header("Digest", format!("{}={}", D::NAME, digest))
             .signature(config, key_id, f)
+            .await
             .map(|c| DigestClient::new(c, v))
     }
 }
diff --git a/http-signature-normalization-actix/src/lib.rs b/http-signature-normalization-actix/src/lib.rs
index 28208b0..bea96fd 100644
--- a/http-signature-normalization-actix/src/lib.rs
+++ b/http-signature-normalization-actix/src/lib.rs
@@ -146,10 +146,13 @@
 //! }
 //! ```
 
-use actix_web::http::{
-    header::{HeaderMap, InvalidHeaderValue, ToStrError},
-    uri::PathAndQuery,
-    Method,
+use actix_web::{
+    error::BlockingError,
+    http::{
+        header::{HeaderMap, InvalidHeaderValue, ToStrError},
+        uri::PathAndQuery,
+        Method,
+    },
 };
 use chrono::Duration;
 use std::{collections::BTreeMap, fmt::Display, future::Future};
@@ -213,20 +216,36 @@ pub trait SignatureVerify {
 }
 
 /// A trait implemented by the Actix Web ClientRequest type to add an HTTP signature to the request
+#[async_trait::async_trait(?Send)]
 pub trait Sign {
     /// Add an Authorization Signature to the request
-    fn authorization_signature<F, E, K>(self, config: &Config, key_id: K, f: F) -> Result<Self, E>
+    async fn authorization_signature<F, E, K>(
+        self,
+        config: &Config,
+        key_id: K,
+        f: F,
+    ) -> Result<Self, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         Self: Sized;
 
     /// Add a Signature to the request
-    fn signature<F, E, K>(self, config: &Config, key_id: K, f: F) -> Result<Self, E>
+    async fn signature<F, E, K>(self, config: &Config, key_id: K, f: F) -> Result<Self, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
         Self: Sized;
 }
diff --git a/http-signature-normalization-actix/src/sign.rs b/http-signature-normalization-actix/src/sign.rs
index 27d1157..204abd8 100644
--- a/http-signature-normalization-actix/src/sign.rs
+++ b/http-signature-normalization-actix/src/sign.rs
@@ -1,44 +1,64 @@
 use actix_web::{
     client::ClientRequest,
+    error::BlockingError,
     http::header::{InvalidHeaderValue, ToStrError},
+    web,
 };
 use std::fmt::Display;
 
 use crate::{create::Signed, Config, Sign};
 
+#[async_trait::async_trait(?Send)]
 impl Sign for ClientRequest {
-    fn authorization_signature<F, E, K>(
+    async fn authorization_signature<F, E, K>(
         mut self,
         config: &Config,
         key_id: K,
         f: F,
     ) -> Result<Self, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
+        Self: Sized,
     {
-        let signed = prepare(&self, config, key_id, f)?;
+        let signed = prepare(&self, config, key_id, f).await?;
         signed.authorization_header(self.headers_mut())?;
         Ok(self)
     }
 
-    fn signature<F, E, K>(mut self, config: &Config, key_id: K, f: F) -> Result<Self, E>
+    async fn signature<F, E, K>(mut self, config: &Config, key_id: K, f: F) -> Result<Self, E>
     where
-        F: FnOnce(&str) -> Result<String, E>,
-        E: From<ToStrError> + From<InvalidHeaderValue>,
+        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+        E: From<BlockingError<E>>
+            + From<ToStrError>
+            + From<InvalidHeaderValue>
+            + std::fmt::Debug
+            + Send
+            + 'static,
         K: Display,
+        Self: Sized,
     {
-        let signed = prepare(&self, config, key_id, f)?;
+        let signed = prepare(&self, config, key_id, f).await?;
         signed.signature_header(self.headers_mut())?;
         Ok(self)
     }
 }
 
-fn prepare<F, E, K>(request: &ClientRequest, config: &Config, key_id: K, f: F) -> Result<Signed, E>
+async fn prepare<F, E, K>(
+    request: &ClientRequest,
+    config: &Config,
+    key_id: K,
+    f: F,
+) -> Result<Signed, E>
 where
-    F: FnOnce(&str) -> Result<String, E>,
-    E: From<ToStrError>,
+    F: FnOnce(&str) -> Result<String, E> + Send + 'static,
+    E: From<BlockingError<E>> + From<ToStrError> + std::fmt::Debug + Send + 'static,
     K: Display,
 {
     let unsigned = config.begin_sign(
@@ -49,7 +69,7 @@ where
 
     let key_id = key_id.to_string();
 
-    let signed = unsigned.sign(key_id, f)?;
+    let signed = web::block(move || unsigned.sign(key_id, f)).await?;
 
     Ok(signed)
 }