On Mon, Feb 11, 2013, Naveen Nathan wrote:

> 
> When I specify intermediate values I only set the h[8], Nl, Nh values.
> The num is set to 0, and md_len to SHA256_DIGEST_LENGTH. It is unclear
> to me what the Nl and Nh values represent. Without them, I was unable
> to compute the correct digests for certain test vectors in my proof of
> concept. I tried to follow the md32_common.h which computes the
> merkle-damgard construction using SHA. However, it's unclear what Nl,Nh
> represent and why they are necessary. The SHA256 spec only discusses
> values in h[8].
> 

I believe Nh/Nl are the running bit count. This is needed for the final block
padding.

Steve.
--
Dr Stephen N. Henson. OpenSSL project core developer.
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