[Openid-specs-ab] JWS/A : ECDSA signature byte length

Axel.Nennker at telekom.de Axel.Nennker at telekom.de
Mon May 28 08:26:17 UTC 2012


The digest length of SHA-256 is 32 bytes and together with this paragraph "The security strength associated with the ECDSA digital signature process is no greater than the minimum of the security strength associated with the bit length of n and the security strength of the hash function that is employed. Both the security strength of the hash function used and the security strength associated with the bit length of n shall meet or exceed the security strength required for the digital signature process." Of 
http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf

This seems to imply 32 bytes if sha-256 is used.

-----Original Message-----
From: openid-specs-ab-bounces at lists.openid.net [mailto:openid-specs-ab-bounces at lists.openid.net] On Behalf Of hideki nara
Sent: Monday, May 28, 2012 3:43 AM
To: openid-specs-ab at lists.openid.net
Subject: [Openid-specs-ab] JWS/A : ECDSA signature byte length

Hi all,

I'm developing JWS library with C# and Python.
Could someone please describe why the byte length of ECDSA signature, r and s,  is 32 ?

Thanks in advance.
---
hdknr
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