[openssl-users] Is it mandatory to reverse windows signature while doing verification in OpenSSL?

Rishabh K Dubey rishabh.dubey at igate.com
Thu Apr 2 08:46:22 UTC 2015

Thanks Jeff for quick confirmation.


-----Original Message-----
From: openssl-users [mailto:openssl-users-bounces at openssl.org] On Behalf Of Jeffrey Walton
Sent: Thursday, April 02, 2015 1:25 PM
To: OpenSSL Users List
Subject: Re: [openssl-users] Is it mandatory to reverse windows signature while doing verification in OpenSSL?

> We have signed data on Win 7 using Crypto APIs and generated 
> signature. We have observed this signature data needs to be reversed 
> for verification using OpenSSL. If we reverse signature data and pass 
> it to OpenSSL verification command then OpenSSL verifies it 
> successfully. We wanted to confirm, whether such reversing of 
> signature bytes is valid operation or not. Thanks in advance.
As Tom said, reversing the bytes is quite common when interop'ing with MS CAPI. See, for example, http://www.google.com/search?q=ms+capi+reverse+bytes.

For the longest time, it was the only library I was aware that you had to be mindful of the endian issues. Poly1305 is now a similar island.
Crypto++'s Integer class recently modified to take the little endian
strings and byte arrays for testing straight from Bernstein's parameters.

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