[dv/hmac] Add url to NIST vectors
diff --git a/hw/dv/sv/nist_vectors/README.md b/hw/dv/sv/nist_vectors/README.md
index 794c2a3..67bb5ee 100644
--- a/hw/dv/sv/nist_vectors/README.md
+++ b/hw/dv/sv/nist_vectors/README.md
@@ -12,3 +12,7 @@
* **parse_sha**: A method to parse sha vectors files. Return an array of
nist_vectors_t.
+### SHA256 vectors
+The SHA256LongMsg.rsp and SHA256ShortMsg.rsp are test vector files downloaded from the NIST
+website:
+'''https://csrc.nist.gov/Projects/Cryptographic-Algorithm-Validation-Program/Secure-Hashing#shavs'''
