Subject: [P2PSIP] What is the point of SHA256 self-signed digest?

From: "Michael Chen" <[email-masked]>
Date: Fri, 27 May 2011 13:51:24 -0700

Hi,

In the base-13 draft section 10.1, it mandates the support of SHA1 and
SHA256 self-signed digest for generating NodeId. However, in the same
section, it also defines the "node-id-length" to be no more than 160
bits (SHA1). This means if SHA256 is used, the NodeId will be truncated
to 160 bit or less.

Why mandate a crippled SHA256 that offers no added strength than SHA1?
Consider removing it altogether. If 128-bit is good enough for NodeId,
then 160-bit good enough for self-signed certs.

I would also recommend adding language of "recommending" the use of SHA1
for all signer-id-hash in signature for the same reason. It's another
topic.

Thanks

--Michael

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From: Eric Rescorla <[email-masked]>
Date: Fri, 27 May 2011 13:54:33 -0700

> Why mandate a crippled SHA256 that offers no added strength than SHA1?

I don't believe this is true. There is ample evidence that SHA-1 is
substantially
weaker than its output length, whereas a truncated SHA-256 is quite possibly
(likely?) stronger.

-Ekr