Harel

96 reputation

bio	website
	location	Israel
	age	34
visits	member for	8 months
	seen	May 7 at 18:30
stats	profile views	4

Security specialist with a focus on cryptography (mainly the applicative side of things), cryptanalysis, software protection, software obfuscation, device security.

	96 reputation	bio	website		visits	member for	8 months
6 badges		location	Israel		seen	May 7 at 18:30

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Sep 21	awarded	Commentator
Sep 21	comment	How to plot the distribution of a ciphertext? If you're using python, I'd recommend using matplotlib's pcolor function to display a colored 2D matrix showing the values in the digraph (dibyte) histogram/distribution.
Sep 20	revised	Design criteria for AES small wording and typo fix
Sep 20	comment	Design criteria for AES Agreed. This is why I started with that definition but then later on moved to the Linear Property (LP) of the S-Box. Even if a function is not linear (in your definition too) it can still be "almost linear" (high LP value) and what would be bad.
Sep 20	answered	Design criteria for AES
Sep 17	comment	Encryption scheme with equivalent keys? The very existence of equivalent keys is not a secret in this envisioned scheme. It's deriving new additional keys or "merging" equivalent keys to produce new ones that should be difficult/impossible to an attacker. The problem to be solved, basically, and without dragging you all into too much detail, is within the realm of Conditional Access or DRM systems, where different users need to decrypt the same content (encrypted once for all of them), but using keys that are traceable back to them. As noted above, broadcast encryption schemes can handle this in some settings.
Sep 16	comment	Encryption scheme with equivalent keys? Thanks, but schemes based on broadcast encryption key distribution are another matter, and have their own practical considerations. I was still wondering if schemes/algorithms based "simply" on equivalent keys, as I defined, are possibles. Maybe the answer is negative.
Sep 15	comment	Encryption scheme with equivalent keys? Thanks - I'll have to think deeper about your answer, but for now, this is why I want requirement 5: if this were some scheme where equivalent keys were handed out, one to each user/customer, and these were leaked, then they could be traced. But if there's such an intermediate value, this kind of traitor tracing property is lost. In your example, if such a traitor leaked the 128 bits used as the AES key, it wouldn't be traceable to him.
Sep 15	awarded	Student
Sep 15	revised	Encryption scheme with equivalent keys? deleted 2 characters in body
Sep 15	asked	Encryption scheme with equivalent keys?
Sep 15	awarded	Analytical
Sep 14	awarded	Teacher
Sep 14	answered	Why RSA can't handle numbers above 76?
Sep 14	awarded	Editor
Sep 14	comment	How to decrypt AES in CBC @Paulo, I edited my answer above with text from the comment that seemed to satisfy angelo. I hope that's better now.
Sep 14	revised	How to decrypt AES in CBC added 439 characters in body
Sep 11	awarded	Supporter
Sep 11	comment	How to decrypt AES in CBC AES is too complex for you to do with pen and paper (well, it could in theory be done but really it's not for the faint of heart). Whoever gave you this task wasn't expecting you to do the AES block cipher itself using pen and paper.
Sep 11	comment	How to decrypt AES in CBC The title of your questions asks about decrypting AES using CBC mode operation. In which case you should be using AES, P_t = AES-128-DEC_k(C_t) XOR C_{t-1}. AES decryption is available in many crypto libraries, and even online here: link for example.