Cryptography July 2006

cryptography@lists.squeakfoundation.org

9 participants
14 discussions

IPSec ESP with AES
by Ron Teitelbaum 11 Jul '06

11 Jul '06

Hi All, Has anyone attempted IPSec Encapsulating Security Payload (ESP), it looks like we have most of what is needed to get this to work. I don't want to attempt it if it's already done. Also there is a possibility that this work will require some minor network VM changes for ESP headers (although I'm just getting started so I'm not sure about that), since the tcp packets are handled in primitives. So has anyone written an ESP tcp socket already? And will anyone in the VM or Network Group volunteer to help with VM changes to get this done? Thanks, Ron Teitelbaum President / Principal Software Engineer US Medical Record Specialists Ron(a)USMedRec.com Squeak Cryptography Team Leader

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Re: isProperlyPadded
by Chris Muller 07 Jul '06

07 Jul '06

> Since isProperlyPadded assumes that that was some padding the error > seems > unnecessary. > ... > To make it more clear if a byte array is not padded then the > unpaddedSize is > self size. Hi Ron, I believe the check in #unpaddedSize is proper, let me explain. Any application must know if it is dealing with a block or stream cipher, therefore it knows if padding is necessary. I think you agree with this because you said: > Since isProperlyPadded assumes that that was some padding.. In other words, isProperlyPadded knows nothing about whether a ByteArray *is* padded, you only call it if you KNOW it's supposed to be padded and then it will tell you if it is padded properly. If padding is not necessary (stream cipher), the program should not be asking for the #unpaddedSize at all. If padding is necessary then Nils and Bruce say any improper padding should be treated as an authentication error. If the program asks for the #unpaddedSize for a message that was not properly padded, simply returning "self size" would be erroneous and the program would then be making improper assumptions about the message. Regards, Chris

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FW: isProperlyPadded
by Ron Teitelbaum 07 Jul '06

07 Jul '06

Hit send by accident before I finishing editing! To make it more clear if a byte array is not padded then the unpaddedSize is self size. What do you think? Ron Teitelbaum _____ From: Ron Teitelbaum [mailto:Ron@USMedRec.com] Sent: Thursday, July 06, 2006 11:08 PM To: 'Cryptography Team Development List' Subject: isProperlyPadded Chris, I ran into your padding methods which put the remainder size in each empty space after the real data. I have a problem with ByteArray>>unpaddedSize "If I was padded by a BlockCipher, answer the size of the original plaintext." self isProperlyPadded ifFalse: [ CryptographyError signal: 'Authentication failure (improperly padded!)' ]. ^ self size - self last Since isProperlyPadded assumes that that was some padding the error seems unnecessary. Shouldn't this say: ByteArray>>unpaddedSize "If I was padded by a BlockCipher, answer the size of the original plaintext." self isProperlyPadded ifFalse: [^self size]. ^ self size - self last

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isProperlyPadded
by Ron Teitelbaum 07 Jul '06

07 Jul '06

Chris, I ran into your padding methods which put the remainder size in each empty space after the real data. I have a problem with ByteArray>>unpaddedSize "If I was padded by a BlockCipher, answer the size of the original plaintext." self isProperlyPadded ifFalse: [ CryptographyError signal: 'Authentication failure (improperly padded!)' ]. ^ self size - self last Since isProperlyPadded assumes that that was some padding the error seems unnecessary. Shouldn't this say: ByteArray>>unpaddedSize "If I was padded by a BlockCipher, answer the size of the original plaintext." self isProperlyPadded ifFalse: [^self size]. ^ self size - self last

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Cryptography July 2006