[squeak-dev] Crypto RSAWithSHA1 sign

Rob Withers reefedjib at gmail.com
Tue Sep 21 16:06:49 UTC 2010


Hi Denis,

I originally wrote the v15 signature methods in April of 2007.  I am currently trying to download the PKCS#11 V2.30 doc to verify, but IIRC there are more than one signature algorithm defined for RSA.  I don't recall why I chose v15.  Perhaps Java is using another RSA signature function.

There are no explicit tests for this signature.  There is a test inside of the CryptoX509Test  (#verifySHA1WithRSAEncryptionFromParentCertificate: ), but it isn't used as the certificate that exposed it has expired and so is failing.  I removed that certificate test.

Let's talk bytes...the way this works in Squeak is that the RSA pads the SHA1 hashed message and encrypts it.

v15SignMessage: aMessage

 ^ self v15SignMessageHash: (SHA1 hashMessage: aMessage).

and

v15SignMessageHash: encodedMsg

 | padded toBeSigned |
 padded := ByteArray new: (256 - encodedMsg size - 3) withAll: 255.
 toBeSigned := #(0) asByteArray, #(1) asByteArray, padded, #(0) asByteArray, encodedMsg.
 ^ (self crypt: toBeSigned asInteger) asByteArray.

Presumably the #crypt: function will be the same in Java and Squeak given the same key.  So if there are 2 different signature functions in RSA, I would suspect that the padding would be different.

Still trying to download the spec....

What do you think?

Cheers,
Rob


From: Denis Kudriashov 
Sent: Tuesday, September 21, 2010 11:21 AM
To: The general-purpose Squeak developers list 
Subject: [squeak-dev] Crypto RSAWithSHA1 sign


Hello 

Is somebody use Cryptography for RSA with SHA1 digital signature?

I try do same result as I hava in java programm
I have rsa private key as smalltalk object. It has same values as java private key object.

But code

privateKey v15SignMessage: message asByteArray  .

returns me wrong result. Its differ from java working test



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