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Aug
5
comment Does it necessarily mean that an RSA moduli generated with poor randomness is not random?
By doing exactly what they did in the paper you're talking about : calculating their gcd. In a truly random sequence of semiprimes the gcd found would be 1 with high probability...
Aug
5
comment Does it necessarily mean that an RSA moduli generated with poor randomness is not random?
Short answer is yes : If the PRNGs had been properly seeded it would have been very unlikely that two moduli share a non-trivial factor. Said otherwise the moduli generated with in that way are a particular subset (understand here non-random) of the semi-primes of a given size
Jul
23
comment Why is it a security problem that two RSA moduli are not co-prime?
Two links that you might find useful to understand exactly how often does that happen in real life freedom-to-tinker.com/blog/nadiah/… eprint.iacr.org/2012/064
Jul
23
comment Is there any weak message for an ECDSA signature?
You're right, I didn't read the question well enough. That being said I think the point is still valid since there was no technical reasons for keeping the messages short and that limitation could well have been lifted in the future
Jul
23
answered Is there any weak message for an ECDSA signature?
Jul
15
comment How can Alice prove that a message has not been tampered with?
Sorry I was in a hurry I'll flesh out my answer when I get the chance
Jul
15
answered How can Alice prove that a message has not been tampered with?
Jul
14
comment Encrypted counter as IV in CBC mode encryption using same key
If the IV was encrypted using a separate key then taking advantage of this scheme would be equivalent to somehow predict the values of an AES-CTR based PRNG. Since you're using the same key the reasoning doesn t apply but is there a reason why you can t derive 2 keys from your initial key and then go about your buisness ?
Jul
13
comment Is OpenPGP vulnerable to the “crypto doom principle”?
Actually Sign-Then-Encrypt is worse than its Symmetric counter : in the public key setting, you can forward messages to make them appear having come from the original signer
Jul
10
comment Selecting bijective functions for permutations
I would also suggest taking a look at the permutation inside Keccak, it doesn't use any S-Boxes either...
Jul
5
comment Is this ECC encryption key sharing method okay?
The key being used here is always the same which means that you're basically doing ECDH followed by regular symmetric encryption. Thus you need to be careful as to how much data you're going to encrypt with your key.
Jun
26
answered How do you find the inverse degree of a hash function?
Jun
13
comment Is it possible to cryptographically prove when was the last time a ciphertext was decrypted/encrypted?
Given that you can make multiple copies of the same document I don't really see how you can be assure that a document wasn't encrypted/decrypted.
Jun
6
answered Composition of block ciphers and 3DES
Apr
29
comment Custom crypto library in C
I don't understand how the sleep function can help you prevent timing attacks : how do you know how much time you need to sleep ? Also if your using the worst case running time as a reference you need to know what it is precisely on the platform your library is running which requires fine tuning after every install which. May I ask why you're not using and existing library (NaCl, openssl ect) ?
Apr
10
answered EC equivalent for RSA-OAEP
Apr
9
answered Signature schemes for underpowered devices (8bit microcontroller)
Mar
14
revised Is this encryption algorithm build from MD5 secure?
added reference to Hash CFB
Mar
6
comment Is this encryption algorithm build from MD5 secure?
Look at the effect of flipping a bit in the last ciphertext block, if I understood the algorithm correctly this only flips the corresponding bit in the last plaintext block which might be useful if you know the format of the message even if you don't know the content
Mar
6
answered Is this encryption algorithm build from MD5 secure?