Subject: [Classpathx-crypto] NESSIE RSA-PSS submission

From: "Raif S. Naffah" <[email-masked]>
Date: Sun, 06 Jan 2002 09:52:29 +1100

Gentlemen,

while implementing this scheme in Java, i found an inconsistency in the 
specification of the EMSA-PSS-Decode(M, EM, emBits) primitive (document B 
of your submission, page 11), at step #10.

this should read "...or if the octet at position emLen -hLen -sLen -2 is 
not equal to 01..." and not "...emLen -hLen -sLen -1."

cheers;
rsn

---

From: "Jakob Jonsson" <[email-masked]>
Date: Thu, 10 Jan 2002 11:20:21 +0100

Hi Raif,

I think the inconsistency lies in how you define the leftmost position of an
octet string; this could be either "position 0" (as in C and Java) or
"position 1". We have adopted the second convention; the octet on position n
is the nth leftmost octet rather than the (n+1)st leftmost octet. The length
of the PS string preceding the 01 octet is emLen-hLen-sLen-2, so the 01
octet is on position emLen-hLen-sLen-1.

Yet, I admit that this convention should have been explicitly stated in the
document.

Best regards,
Jakob Jonsson
RSA Laboratories

----- Original Message -----
From: "Raif S. Naffah" <[email-masked]>
To: <[email-masked]>; <[email-masked]>
Cc: "GNU Crypto Developers" <[email-masked]>; "Paulo S. L. M.
Barreto" <[email-masked]>
Sent: Saturday, January 05, 2002 11:52 PM
Subject: NESSIE RSA-PSS submission

---

From: "Raif S. Naffah" <[email-masked]>
Date: Sat, 12 Jan 2002 07:23:02 +1100

>octet is on position emLen-hLen-sLen-1.

yes. it definitely makes sense.  i was in "java mode" too deep to see 
another explanation.

>Yet, I admit that this convention should have been explicitly stated in the

thanks for taking the time to respond.

FYI, the soon to be released GNU library will include a full implementation 
of the RSA-PSS scheme with spport for both SHA and RIPEMD160 as underlying 
hash functions for the MGF.

cheers;
rsn

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