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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Oct
1
answered Hybrid encryption with RSA and AES versus spliting into multiple RSA messages?
Oct
1
comment Hybrid encryption with RSA and AES versus spliting into multiple RSA messages?
Yes RSA can do signature. But in your description, you are using RSA for encryption. Breaking something RSA-signed into chunks is unsafe, in particular the chunks can be reordered. And again the question does not suggest in any way that RSA signature is employed.
Oct
1
comment Understanding elliptic curve encryption
You do not have enough familiarity with modular arithmetic to tackle Elliptic Curves (much less Elliptic Curve Encryption or other forms of Elliptic Curve Cryptography), if you do not understand that $y=4$ is a solution to $1\equiv y^2\pmod 5$. Hint: apply the definition of $a\equiv b\pmod c$, which is that $c$ divides $b-a$.
Oct
1
comment How broken is a xor of two LCGs?
@Ilmari Karonen: the modulus you suggest does solve the issue that the top bit is badly biased, and blocks D.W.'s attack. However it opens to other even more devastating attacks, based on the fact that low-order bits now seldom influence high-order ones.
Sep
30
comment Is it possible to create an open-source SecurID?
Here's a sate of the art commercial solution; another
Sep
30
comment Is it possible to create an open-source SecurID?
@Ricky Demer: bluetooth is fast and bidirectional, and solves any bandwidth problem in either direction. Sound from PC speaker to microphone on token also works. As to the solution to a MitM threat, I'm not sure I get what you are thinking of. With a few hundred bytes to the token, we can check (with public key) and display on the token the host's ID, date, transaction amount and purpose, that the holder of the token can check before committing to key in the code shown by the token. That's in addition to a PIN on the token (the what you know factor).
Sep
30
revised Is it possible to create an open-source SecurID?
Readable summary of conclusions as intro.
Sep
30
comment Is it possible to create an open-source SecurID?
@Ricky Demer: Yes, RSA has several drawbacks here: relatively high cryptogram size, key size, and computational resources on the token side. I cited it because it is unquestionably public domain, simple, and well established. I have no idea of the IP status of ECC-based Cramer-Shoup, much less in the context of an identification token.
Sep
29
revised Is it possible to create an open-source SecurID?
Credit to "La grenouille"
Sep
29
revised Is it possible to create an open-source SecurID?
Credit to "La grenouille"
Sep
29
answered Is it possible to create an open-source SecurID?
Sep
29
comment Why was the winner of the AES competition not a Feistel cipher?
@J.D: I see your point that if I rewrite MARS in my definition of Feistel, the ⊕ group operations that I use are not the same at each round, and the resulting cipher has much more rounds than claimed in the normal description of MARS.
Sep
29
revised Why was the winner of the AES competition not a Feistel cipher?
Clarify
Sep
29
comment Why was the winner of the AES competition not a Feistel cipher?
@J.D.: I agree that Serpent and RC6 are not Feistel, but MARS? The authors wrote that MARS is a type-3 Feistel cipher, and if there is any obstacle to putting it in that framework, I keep missing it.
Sep
29
revised Why was the winner of the AES competition not a Feistel cipher?
RC neither
Sep
29
comment Why was the winner of the AES competition not a Feistel cipher?
@Reid: my mistake, you are right. I fixed the question. Thanks a lot! I had used the drawing in the wikipedia article, rather than the complete description.
Sep
29
revised Why was the winner of the AES competition not a Feistel cipher?
Serpent can't be turned into a Feistel cipher
Sep
29
asked Why was the winner of the AES competition not a Feistel cipher?
Sep
29
revised How to attack a fixed LCG with partial output?
Fix size of R
Sep
29
answered How to attack a fixed LCG with partial output?