# TLS Extension signature_algorithms values

I hate asking for a reference, but I'm having a hard time finding this.

The iana page on tls extensions just links me back to rfc5246 where it only has the following values:

enum {
none(0), md5(1), sha1(2), sha224(3), sha256(4), sha384(5),
sha512(6), (255)
} HashAlgorithm;

enum { anonymous(0), rsa(1), dsa(2), ecdsa(3), (255) }
SignatureAlgorithm;


I've got a client hello that I'm looking at here with the following signature and hash extension:

000d 0014 0012 0403 0804 0401 0503 0805 0501 0806 0601 0201

Where can I find a reference for what these refer to?

• Can you please ASN.1 decode the values you posted? – SEJPM Jun 15 '18 at 9:07
• @SEJPM It's not ASN.1! – Thomas Pornin Jun 15 '18 at 11:27

• 000d is the identifier for the "signature algorithm" extension.
• 0014 is the extension contents length (in bytes).
• 0012 is the length of the list of values in the extension (because the extension is defined as a list of values, and lists in TLS message encodings take an explicit header that gives the list length in bytes).