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Moderator♦ pro tempore on French Language, Computer Science and Software Recommendations. I'm also a unix amateur, and a developer on embedded systems with a computer science background and security leanings by trade.

Avatar picture slightly adapted from a photo by Luridiformis (Zonda Grattus).


5h
comment How much would it cost in U.S. dollars to brute force a 256 bit key in a year?
Your math is completely wrong.
Mar
26
comment zendo data size restrictions
How do you know how the keystream is generated? I don't see that in the TC article. Granted, not all phones have a hardware RNG, so they must have a fallback — and that's probably happening at the OS level, behind the scenes of /dev/random, not under control of their application.
Mar
25
comment Cycles in SHA256
Your other question about collisions on 256-bit strings is answered here (for SHA-512 but the principle is the same).
Mar
23
comment Is it possible to make time-locked encrytion algorithm?
You can't know that adversaries haven't kept a cache of the web page.
Mar
20
comment Creating a new cipher!
This is a questions and answers site, not a site to review designs. If you want your system reviewed, submit it to a peer-reviewed journal.
Mar
19
comment can you help us find a method to read the secret code in this image
This does not appear to be about cryptography. If there's any encryption, it isn't apparent. There may be steganography, but since you're asking about solving one problem rather than looking for a teachable moment, you should feel more at home on Puzzling than on a site for scientists and engineers.
Mar
17
comment Practical strength of non-2^n RSA key lengths
@sampablokuper The cost for the attacker of a bug in the attacker's crypto library is negligible. The situation is not at all symmetric. Increasing the test coverage requirement costs the defender a lot more than it costs the attacker. That contributes to proving the saying false.
Mar
17
comment Is RSA-OAEP secure when e=3?
See also What security authorities and standards reject e=3 in RSA, when, and with what rationale?
Mar
15
comment decrypt a saml 2.0 response having aes 128 and rsa
I'm voting to close this question as off-topic because it is a programming question with no direct cryptographic content. You should ask on Stack Overflow, but you need to POST YOUR CODE.
Mar
12
comment What is the difference between a hash and a permutation?
This is so unrelated to the question that it's completely irrelevant. Keep in mind that this site is about cryptography. The words hash and permutation do not have the same meaning there as in data structures.
Mar
9
comment CTR HMAC SHA256 implementation
@JohnSmith I'm not sure what you're describing here but this is not HMAC. If you were using HMAC, you wouldn't be talking about IPAD and OPAD — they're purely internal to the HMAC primitive.
Mar
9
comment CTR HMAC SHA256 implementation
@JohnSmith Because combining them is tricky (see the threads I link to). “Creating your own” is bad because you're using primitives whose behavior is not well-known, so it's delicate at best to use them correctly. In the case of HMAC+CTR, it's known that it's a tricky combination, and neither encrypt-then-mac nor mac-then-encrypt can be used without being very very careful. Using a known authenticated encryption mode frees you of this concern.
Mar
9
comment CTR HMAC SHA256 implementation
@JohnSmith But combining them makes a new mode, AES-CTR+HMAC-SHA256.
Mar
9
comment Known plaintext, unknown 128 bit block cipher
With modern ciphers, it's impossible to reverse engineer an encryption algorithm by looking at (plaintext, ciphertext) pairs. You need to reverse engineer the encryption or decryption code instead.
Mar
8
comment Standard serialization format for libsodium-based messages
I'm voting to leave this question open because it is to a large extent about choosing the right kind of cryptographic primitive and passing it appropriate arguments. It isn't just an implementation question but also a cryptographic protocol design question.
Mar
8
comment Standard serialization format for libsodium-based messages
You've missed the point of the question, which is to store a cookie in an untrusted location, so that the cookie needs to be at least authenticated upon reading.
Mar
7
comment Will SHA1 or Other Hash Functions Ever Contain Quotes
I'm voting to close this question as off-topic because it is about programming, with cryptography only involved tangentially. It would be on-topic on Stack Overflow.
Feb
27
comment Hashes and Ciphers
Have you lookd up the definitions (e.g. on Wikipedia)? What part don't you understand? It isn't really possible to meaningfully answer “what's the difference between a fish and a bicycle or a railway or a truck”.
Feb
25
comment How does hash function in Elgamal signature scheme prevent existential forgery attack?
This is wrong. Hashing does not participate in identifying the origin of the message at all. It is used as a proxy for the integrity of the message but it's the calculation of the signature from the hash that handles the authenticity.
Feb
25
comment How to choose an algorithm
If You’re Typing the Letters A-E-S Into Your Code You’re Doing It Wrong. That being said, you do need to know how to choose algorithms if you're designing protocols, but there's no miracle: you need to study the topic for a while before you can make design decisions.