diff --git a/src/crypto/hash.h b/src/crypto/hash.h
index 10b0373..783ba57 100644
--- a/src/crypto/hash.h
+++ b/src/crypto/hash.h
@@ -31,6 +31,9 @@ namespace eoskeygen {
 
 sha256_t* sha256(const unsigned char *data, std::size_t len, sha256_t* out);
 
+// sha256 double.
+sha256_t* sha256d(const unsigned char *data, std::size_t len, sha256_t* out);
+
 ripemd160_t* ripemd160(const unsigned char *data, std::size_t len, ripemd160_t* out);
 
 } // namespace eoskeygen
diff --git a/src/crypto/openssl/hash.cpp b/src/crypto/openssl/hash.cpp
index 08cf360..0e26334 100644
--- a/src/crypto/openssl/hash.cpp
+++ b/src/crypto/openssl/hash.cpp
@@ -31,6 +31,11 @@ sha256_t* sha256(const unsigned char *data, std::size_t len, sha256_t* out) {
 	return (sha256_t *) SHA256(data, len, out->data);
 }
 
+sha256_t* sha256d(const unsigned char *data, std::size_t len, sha256_t* out) {
+	SHA256(data, len, out->data);
+	return (sha256_t *) SHA256(data, 32, out->data);
+}
+
 ripemd160_t* ripemd160(const unsigned char *data, std::size_t len, ripemd160_t* out) {
 	return (ripemd160_t *) RIPEMD160(data, len, out->data);
 }