Repair sentence fragment in message authentication section

security/crypto.rst

@@ -388,8 +388,10 @@ attack”—see the exercises for more details.
 There have been several common cryptographic hash algorithms over the
 years, including Message Digest 5 (MD5) and the Secure Hash Algorithm
 (SHA) family. Weaknesses of MD5 and earlier versions of SHA have been
-known for some time, which led NIST to recommend using SHA-3 in 2015.
-generating an encrypted message digest, the digest encryption could use
+known for some time, which led NIST to develop and recommend a family
+of algorithms known as SHA-3 in 2015.
+
+When generating an encrypted message digest, the digest encryption could use
 either a secret-key cipher or a public-key cipher. If a public-key
 cipher is used, the digest would be encrypted using the sender’s private
 key (the one we normally think of as being used for decryption), and the