diff --git a/Cargo.lock b/Cargo.lock
index 695725121..f3b5dd54c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -166,6 +166,7 @@ dependencies = [
  "tor-dirmgr",
  "tor-error",
  "tor-guardmgr",
+ "tor-llcrypto",
  "tor-netdoc",
  "tor-persist",
  "tor-proto",
diff --git a/crates/arti-client/Cargo.toml b/crates/arti-client/Cargo.toml
index cf1456d9d..b127aae1c 100644
--- a/crates/arti-client/Cargo.toml
+++ b/crates/arti-client/Cargo.toml
@@ -18,7 +18,16 @@ default = ["tokio", "native-tls"]
 #   * Features that are testing-only
 #   * Features which are select a particular implementation or build flag and
 #     which therefore are not strictly additive.
-full = ["tokio", "async-std", "native-tls", "rustls", "tor-rtcompat/full", "tor-proto/full", "tor-netdoc/full", "tor-dirmgr/full"]
+full = [
+    "tokio",
+    "async-std",
+    "native-tls",
+    "rustls",
+    "tor-rtcompat/full",
+    "tor-proto/full",
+    "tor-netdoc/full",
+    "tor-dirmgr/full",
+]
 
 async-std = ["tor-rtcompat/async-std"]
 tokio = ["tor-rtcompat/tokio", "tor-proto/tokio"]
@@ -29,11 +38,24 @@ static = ["static-sqlite", "static-native-tls"]
 static-sqlite = ["tor-dirmgr/static"]
 static-native-tls = ["tor-rtcompat/static", "native-tls"]
 
+accel-sha1-asm = ["tor-llcrypto/with-sha1-asm"]
+accel-openssl = ["tor-llcrypto/with-openssl"]
+
 # Enable experimental APIs that are not yet officially supported.
 #
 # These APIs are not covered by semantic versioning.  Using this
 # feature voids your "semver warrantee".
-experimental = ["dirfilter", "experimental-api", "error_detail", "tor-proto/experimental", "tor-cell/experimental", "tor-checkable/experimental", "tor-netdoc/experimental", "tor-dirmgr/experimental", "tor-circmgr/experimental"]
+experimental = [
+    "dirfilter",
+    "experimental-api",
+    "error_detail",
+    "tor-proto/experimental",
+    "tor-cell/experimental",
+    "tor-checkable/experimental",
+    "tor-netdoc/experimental",
+    "tor-dirmgr/experimental",
+    "tor-circmgr/experimental",
+]
 experimental-api = []
 dirfilter = ["tor-dirmgr/dirfilter"]
 error_detail = []
@@ -60,6 +82,7 @@ tor-config = { path = "../tor-config", version = "0.4.0" }
 tor-dirmgr = { path = "../tor-dirmgr", version = "0.4.0" }
 tor-error = { path = "../tor-error", version = "0.3.1" }
 tor-guardmgr = { path = "../tor-guardmgr", version = "0.3.1" }
+tor-llcrypto = { path = "../tor-llcrypto", version = "0.3.1" }
 tor-netdoc = { path = "../tor-netdoc", version = "0.4.0" }
 tor-persist = { path = "../tor-persist", version = "0.4.0" }
 tor-proto = { path = "../tor-proto", version = "0.3.1" }
diff --git a/crates/arti-client/src/lib.rs b/crates/arti-client/src/lib.rs
index 7052d5bea..c10b51bdb 100644
--- a/crates/arti-client/src/lib.rs
+++ b/crates/arti-client/src/lib.rs
@@ -195,6 +195,15 @@
 //! * `static-native-tls` -- link with a static version of `native-tls`. Enables
 //!   `native-tls`.
 //!
+//! ## Cryptographic acceleration features
+//!
+//! Libraries should not enable these by default, since they replace one
+//! implementation with another.
+//!
+//! * `accel-sha1-asm` -- Accelerate cryptography by using an assembly
+//!   implementation of SHA1, if one is available.
+//! * `accel-openssl` -- Accelerate cryptography by using openssl as a backend.
+//!
 //! ## Experimental and unstable features
 //!
 //!  Note that the APIs enabled by these features are NOT covered by semantic
diff --git a/crates/arti/Cargo.toml b/crates/arti/Cargo.toml
index 40d849792..bcfadd6fe 100644
--- a/crates/arti/Cargo.toml
+++ b/crates/arti/Cargo.toml
@@ -25,6 +25,9 @@ static-sqlite = ["arti-client/static-sqlite"]
 static-native-tls = ["arti-client/static-native-tls", "native-tls"]
 journald = ["tracing-journald"]
 
+accel-sha1-asm = ["arti-client/accel-sha1-asm"]
+accel-openssl = ["arti-client/accel-openssl"]
+
 # This feature flag enables experimental features that are not supported. Turning it on may
 # void your API.
 experimental = ["arti-client/experimental"]
diff --git a/crates/arti/src/lib.rs b/crates/arti/src/lib.rs
index 6af26e3df..9c37cb0ab 100644
--- a/crates/arti/src/lib.rs
+++ b/crates/arti/src/lib.rs
@@ -72,6 +72,15 @@
 //! * `static-native-tls` -- Link with a static version of `native-tls`. Enables
 //!   `native-tls`.
 //!
+//! ## Cryptographic acceleration features
+//!
+//! Libraries should not enable these by default, since they replace one
+//! implementation with another.
+//!
+//! * `accel-sha1-asm` -- Accelerate cryptography by using an assembly
+//!   implementation of SHA1, if one is available.
+//! * `accel-openssl` -- Accelerate cryptography by using openssl as a backend.
+//!
 //! ## Experimental features
 //!
 //!  Note that the APIs enabled by these features are NOT covered by semantic