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Jun
29
comment Double the key in block cipher - which approach is better?
Xoring $k_2$ into both then plaintext and the ciphertext is better that xoring it only into one Even Mansour construction
Jun
29
comment Security of this deterministic encryption scheme
Implementing this scheme without a padding oracle isn't trivial, unless the MACed plaintext is already padded.
Jun
29
comment Extracting a WinRAR password
I can't say for sure without having looked at the winrar crypto in detail, but I consider it pretty unlikely since it'd require an unusually dumb mistake. Probably the best you can do is running a program that tests many password candidates, but that's only feasible for simple passwords.
Jun
29
comment Extracting a WinRAR password
Known plaintext attacks don't work against modern ciphers.
Jun
29
comment Block Ciphers - Standardize plain text
@AlexRibeiro CTR produces the key stream by encrypting a sequence of counters. While you compute a key stream consisting of full blocks, you can simply discard the useless final bytes. CTR can do that, since it doesn't pass the ciphertext blocks to the blockcipher when decrypting, instead passing the same counters as when encrypting.
Jun
29
comment Bouncy Castle and Salsa 20
I'm voting to close this question as off-topic because it is a programming problem, not a cryptography problem.
Jun
29
comment How does bitmessage encryption work?
Since somebody creating two public keys with the same address doesn't look like a relevant attack, this only relies on (multi-target) second pre-image resistance, not collision resistance. 160 bits is plenty for that.
Jun
27
comment Getting the encryption/has algorithm used for modem configuration file
The full hash is still visible in the edit history. If you want to get rid of it, you need to contact the stackexchange team.
Jun
27
comment Is algorithm with more than $2^{word size}$ words secure?
Do you assume that the wordsize is half the blocksize?
Jun
26
comment HMAC definition by using only one key
@SEJPM I don't have any plans for writing an answer to this question.
Jun
25
comment Why is HMAC-SHA1 still considered secure?
@user93353 Depends on what you want to achieve. Of course no unkeyed hash is a MAC.
Jun
25
comment Why is HMAC-SHA1 still considered secure?
@user93353 Like I said, the security of HMAC-SHA1 depends on the unknown key. If there is no key or it is known to the attacker, the collisions in SHA1 become a threat. But SHA1 should rarely be used in designs, since there are better alternatives available.
Jun
25
comment Why is HMAC-SHA1 still considered secure?
Should we close this as a duplicate of Is HMAC-MD5 considered secure for authenticating encrypted data?? While this question is about SHA1, not MD5, the answer is nearly the same.
Jun
23
comment what are the most common stream ciphers algorithms?
Salsa20 is relatively common as well, due to its use in NaCl and its derivatives.
Jun
23
comment what are the most common stream ciphers algorithms?
AES in CTR mode.
Jun
22
comment RSA: How effective is this keypair-trash attack
In the duplicate I already wrote that there are $2^{500}$ primes relevant for 1024 bit RSA which has a security of about 80 bits against GNFS. What more do you want? An illustration of how unimaginably huge $2^{500}$ is?
Jun
22
comment How to determine the exponent when using RSA
Similar question RSA Key generation: How is multiplicative inverse computed?
Jun
22
comment How to determine the exponent when using RSA
1) You need multiply with the modular multiplicative inverse instead of dividing. 2) $\mathrm{GCD}(e, \phi) \neq 1$, so your choice of $e$ is incompatible with your choice of $q$.
Jun
22
comment What is more efficient, pairing based cryptography or non pairing based cryptography?
@Nubila You didn't even link the paper you're talking about. You didn't give enough context. Your question isn't answerable like that.
Jun
22
comment What is more efficient, pairing based cryptography or non pairing based cryptography?
@Nubila I just posted two schemes that require pairings, what more do you want?