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Apr
19
comment Why does applying 56-bit DES twice only give 57 bits of security?
@Nova: agreed; the answer now is nice and I up-voted it. It would be even better with "All in all about $2^{56}+2^{56}=2^{57}$ DES operations", to clarify which operations are counted, and because we did not count about $2^{48}$ DES operations that are now necessary, and described.
Apr
19
revised Why does applying 56-bit DES twice only give 57 bits of security?
add "complexity" tag in addition to "meet-in-the-middle-attack"
Apr
19
comment Why does applying 56-bit DES twice only give 57 bits of security?
I looked closer, and indeed we have a close match for that question, though asked in more precise and quantitative terms: Meet-in-the-middle with checking complexity, with a good answer.
Apr
19
revised Why does applying 56-bit DES twice only give 57 bits of security?
include the relevant tag
Apr
19
comment Why does applying 56-bit DES twice only give 57 bits of security?
This basic question is NOT a duplicate of these questions. In fact I do not find it either asked or answered anywhere on CSE. We have a closely related but more complex question, with good answers: Attacking 2DES efficiently.
Apr
19
comment Why does applying 56-bit DES twice only give 57 bits of security?
@CodesInChaos: I would be surprised that distinguished points/cycle finding can work with known plaintext (which seems to be the context of the question, since it is said that DES has 56-bit security, when it has only 55-bit security under chosen-plaintext attack due to DES's complementation property, with $\operatorname{DES}_{k_1}(\operatorname{DES}_{k_2}(M))$ only about 56-bit security, not 57-bit). $\;$ More generally, I'm not sure that I understand what you are thinking about.
Apr
18
answered Key space vs Cardinality of 1024-bit RSA
Apr
18
comment Unlock my ZipCrypto deflate
This is indistinguishable from a request to help cracking someone else's attempt at securing data (poorly, but that's immaterial), and we do not want these.
Apr
18
comment What are application of Cryptography in Algebraic Topology
possible duplicate of What are the links between Cryptography and Algebraic Topology?
Apr
18
comment Is chaotic encryption secure?
I located a review with a section about that chapter. It really is an overview, and totally non-committing.
Apr
18
revised What are the constraints for an IV using AES in CBC mode?
Remove "secure" proposition that was not, or least not recommandable
Apr
17
comment Is chaotic encryption secure?
Count me as fully open to the idea that a chaos-based cryptosystem can be made secure, but highly skeptical that it has any advantage over established cryptosystems.
Apr
17
comment What are application of Cryptography in Algebraic Topology
It is usually mathematic fields that find application in cryptography, rather than the other way around (as asked). Cryptography in turn finds application in even more applied fields, like payment.
Apr
17
awarded  Nice Answer
Apr
17
comment Key space vs Cardinality of 1024-bit RSA
To avoid duplicate moduli we want $p<q$, that about halves the cardinality. And then, what about $e$ ? Setting a fixed $e=3$ reduces the cardinality by a factor of about $4/9$. If $e$ is allowed to vary, and we defined an RSA key as $(p\cdot q,e)$, our cardinality increases (and we should account for equivalent $e$ if very large $e$ are allowed). And then, many practical RSA key generation algorithms only generate primes of a certain form (like, such that $p-1$ and $p+1$ each have a known prime factor of a fixed bit size) and that reduces the cardinality of what they could generate.
Apr
16
comment Why is the call to RSA_generate_key_ex() failing sometimes?
Also, if BN_NUM_OF_RANDOM_BITS is decreased, it becomes possible that bne is 1, which works, but is terminally unsafe. Bottom line: random public exponents are an unneeded complication. $2^{16}+1$ is to public exponents what mainframes are to IBM (nobody gets fired for choosing them). $3$ compares to the Raspberry Pi and an intelligently written program instead of a Business Solutions on top of a random database.
Apr
16
revised Is there a way to use bcrypt with passwords longer than 72 bytes securely?
polish
Apr
16
revised Is there a way to use bcrypt with passwords longer than 72 bytes securely?
Formalize the hash requirements
Apr
15
answered Is there a way to use bcrypt with passwords longer than 72 bytes securely?
Apr
15
comment Is there any method to avoid the differential cryptanalysis?
Duplicate of crypto.stackexchange.com/q/9225/555 , and overly terse.