421 reputation
111
bio website inlovewithcrypto.blogspot.com
location Tehran, Iran
age 26
visits member for 1 year, 9 months
seen 2 days ago

Cryptology student in sharif university of technology.

Me on linkedin Profile.


Nov
15
comment Perfectly secret cipher can leak about the key?
Perfectly secure Public Key encryption is impossible. Because in the theory of computer science it has been proven that any turing machine (even a quantum turing machine) that does not "throw away information" is reversible. An encryption algorithm should not throw away information since the information is required for decryption. As a result, in case of public key encryption we only stand against a computationally bounded attacker. And, the only possible security is computational security.
Nov
14
awarded  Nice Answer
Nov
14
answered How to perform frequency analysis of a substitution cipher using a Base64 alphabet
Nov
14
comment As a cryptographer, what are the things I should care about in my implementation of pairing functions?
I wonder is there a problem with my explanation of question or it is not a matter of interest for the majority of this website's users. I expected much more interested and experienced users in this field. I can't believe there was no answer during these days. (And... am I allowed to post this type of comments?)
Nov
13
answered Perfectly secret cipher can leak about the key?
Nov
10
awarded  Promoter
Nov
10
comment As a cryptographer, what are the things I should care about in my implementation of pairing functions?
@pg1989, an interesting question and answer on crypto.SE related to this topic is here
Nov
10
comment As a cryptographer, what are the things I should care about in my implementation of pairing functions?
@pg1989, I cite the blog post by Steven Galbraith who is, to my knowledge, one of the most well-known researchers in the topic of Elliptic Curves. He apparently indicates that the curves on small characteristics are dead and so the the Type-I pairings because these pairings on fields of large primes are practically inefficient.
Nov
10
revised As a cryptographer, what are the things I should care about in my implementation of pairing functions?
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Nov
9
revised As a cryptographer, what are the things I should care about in my implementation of pairing functions?
edited tags
Nov
8
revised How Secure is a Pronounceable Password? In means of entropy
added 13 characters in body
Nov
8
asked As a cryptographer, what are the things I should care about in my implementation of pairing functions?
Nov
7
comment Crypto-Compression Algorithms?
If we consider the case of unknown-message-attack the attacker won't be aware of the reduction in size because whether the sent message is long and redundant or short and with high entropy is not known to the attacker. Also in case of known-message-attack the reduction in size won't help the attacker to guess anything about the key if we assume that the reduction in size is independent of the key. Therefore your argument look flawed to me.
Nov
7
revised Crypto-Compression Algorithms?
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Nov
7
comment Crypto-Compression Algorithms?
@PaĆ­loEbermann Yes! that's precisely correct. However, the probability distribution of the messages changes after the compression and it would be closer to the uniform distribution which subsequently would result in higher entropy. Therefore, in case of uniform distribution for the message and the key the result of "bigger key space than message space" is deducible from Shannon's Perfect Secrecy Theorem. However, :-| I'm going to admit there shouldn't be such an assumption for any encryption and also that could not help with the crypto-compression thing. Or, maybe I should ponder this more.
Nov
7
revised Crypto-Compression Algorithms?
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Nov
7
comment Crypto-Compression Algorithms?
Maybe the statement falls short because of the term "usually". I'll edit that :). But, an example of such assumptions is a deduction of Shannon's perfect secrecy that demonstrates the "key space" should be bigger than "message space". This is acceptable only in the case that message is fully compressed.
Nov
7
answered Crypto-Compression Algorithms?
Nov
7
comment Crypto-Compression Algorithms?
They are two different questions. I believe you should create another question for the second part.
Nov
7
comment Crypto-Compression Algorithms?
I believe the encryption+channel coding couple is also a non-relevant combination but there exist some schemes such as code-based schemes which use this idea for the purpose of performance. In my opinion the idea of compression+encryption makes more sense since both encryption and compression functions outputs are some kind of data with high entropy.