diff --git a/acme_common/Cargo.toml b/acme_common/Cargo.toml
index ed9e9e9..6d3c9e3 100644
--- a/acme_common/Cargo.toml
+++ b/acme_common/Cargo.toml
@@ -13,7 +13,7 @@ name = "acme_common"
 
 [features]
 default = ["openssl"]
-standalone = []
+standalone = ["ring"]
 
 [dependencies]
 base64 = "0.10"
@@ -23,6 +23,7 @@ handlebars = "2.0.0-beta.2"
 http_req = "0.5"
 log = "0.4"
 openssl = { version = "0.10", optional = true }
+ring = { version = "0.14", optional = true }
 serde_json = "1.0"
 syslog = "4.0"
 time = "0.1"
diff --git a/acme_common/src/crypto.rs b/acme_common/src/crypto.rs
index 441cf6e..e5d4aa8 100644
--- a/acme_common/src/crypto.rs
+++ b/acme_common/src/crypto.rs
@@ -1,9 +1,19 @@
 mod openssl_certificate;
+
+#[cfg(not(feature = "standalone"))]
 mod openssl_hash;
+#[cfg(feature = "standalone")]
+mod standalone_hash;
+
 mod openssl_keys;
 
 pub const DEFAULT_ALGO: &str = "rsa2048";
 
 pub use openssl_certificate::{Csr, X509Certificate};
+
+#[cfg(not(feature = "standalone"))]
 pub use openssl_hash::sha256;
+#[cfg(feature = "standalone")]
+pub use standalone_hash::sha256;
+
 pub use openssl_keys::{gen_keypair, KeyType, PrivateKey, PublicKey};
diff --git a/acme_common/src/crypto/standalone_hash.rs b/acme_common/src/crypto/standalone_hash.rs
new file mode 100644
index 0000000..e52252f
--- /dev/null
+++ b/acme_common/src/crypto/standalone_hash.rs
@@ -0,0 +1,5 @@
+use ring::digest::{digest, SHA256};
+
+pub fn sha256(data: &[u8]) -> Vec<u8> {
+    digest(&SHA256, data).as_ref().to_vec()
+}