Thomas

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	2,579 reputation	bio	website		visits	member for	1 year, 3 months
1320 badges		location	Wellington, New Zealand		seen	15 hours ago

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Feb 21	comment	Why do we assume un-security of communication channel on every cryptography system I suppose because you need cryptography to make those channels secure. And you can't just create a mega-channel and say "this is secure, use this for encrypted communication", because a "secure channel" requires authentication of both parties, which is inherently an individual process.
Feb 20	comment	Implementing PKCS#7 Padding on a Stream of Unknown Length? If you're doing things right (i.e. including a MAC, and so on) it will not cause a security weakness. Including the resource length before sending it is standard practice in network applications, because sometimes, there just isn't any way to unambiguously delimit two consecutive resources - or one resource & the end of stream - based solely on the received data (this is the case here).
Feb 20	comment	Implementing PKCS#7 Padding on a Stream of Unknown Length? "padding 1-16 bytes of data isn't exactly the hardest thing in the world" Padding oracle attacks anyone? Is there any reason you can't send the file length in an encrypted header beforehand?
Feb 19	revised	AES key/ciphertext space sizes see fgrieu's comment
Feb 19	revised	Could use an explanation of the notation for an oracle adversary formatted math
Feb 19	revised	AES key/ciphertext space sizes added 1 characters in body
Feb 19	answered	AES key/ciphertext space sizes
Feb 19	reviewed	Approve suggested edit on Why is RSA encryption significantly faster than decryption?
Feb 18	comment	Why is RSA encryption significantly faster than decryption? Hint: consider the size of "e" compared to the size of "d".
Feb 18	revised	Why is RSA encryption significantly faster than decryption? fixed timing; edited tags
Feb 17	comment	AES encryption with shared IV Point taken. Using a message counter as IV with independent session keys is probably the best solution overall.
Feb 17	comment	AES encryption with shared IV I said "if it's initialized with random bits" (not known to the attacker, i.e. derived from the shared secret obtained upon connection). Of course the zero counter case is a flaw.
Feb 17	comment	AES encryption with shared IV The IV becoming public wouldn't be a security flaw if it's initialized with random bits, since they are all unique and unpredictable (though there is no reason to disclose it).
Feb 16	revised	lfsr wiki excerpt added 79 characters in body
Feb 16	comment	Berlekamp-Massey algorithm: case when sequence length is less than double the length of the LFSR Agreed, LFSR's probably merit a tag for themselves since there's a lot to be said about them. I added it.
Feb 16	wiki	created lfsr excerpt
Feb 16	suggested	suggested edit on lfsr tag wiki excerpt
Feb 16	revised	Berlekamp-Massey algorithm: case when sequence length is less than double the length of the LFSR edited tags
Feb 16	comment	AES encryption with shared IV What are you using as integrity checks? A MAC every packet or every "message" (is there a difference? I suppose you are using TCP so is a "message" defined by your application?) and are the client and server authenticated upon handshake?
Feb 16	comment	AES encryption with shared IV Why do you need to send an IV with every packet to begin with? If you are trying to defend against replay attacks, there are better ways to go about that.