121 reputation
7
bio website
location Israel
age 35
visits member for 2 years, 1 month
seen Jun 1 at 6:16

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


Sep
24
awarded  Autobiographer
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.