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May
19
comment How do we know one-way functions can be iterated?
@fkraiem in a general mathematical point of view, both "input" and "output" of a function can elements of some arbitrary sets. Nothing stringy here. The set of (finite) bit-strings and its subsets are important examples, but not really exclusive ones.
May
1
comment PGP digital signature vs SHA256 HMAC Comparison
keylength.com has some comparisons of key sizes for algorithms.
Apr
25
comment SHACAL-2 vs. AES as underlying block cipher for Secure Hash (aka SHA-256)
Also, you would need to do the key-schedule for each block again, which also adds to the execution time.
Apr
19
comment Why does applying 56-bit DES twice only give 57 bits of security?
@fgrieu I guess we could build the table with only one block of plaintext-ciphertext, and for each of the $2^{48}$ found matches check the second block. This would have work of $2^{57} + 2^{49}$, which I would still consider as 57-bit security.
Apr
15
comment Why is Diffie-Hellman considered in the context of public key cryptography?
@i486 Diffie-Hellman does not directly allow encryption, it is just a key-exchange algorithm (and usually the resulting key should be hashed before being used for anything). You could use that key as a "stream cipher" key stream (i.e. XOR it with a plaintext) and send the result as ciphertext, but then you are actually doing more than just DH.
Apr
12
comment Encryption in which ciphertext is bigger than plaintext?
In cipher designs one usually tries to avoid a (more than constant) increase of the ciphertext.
Apr
4
comment Different implementations of SHA1, which one is correct?
@MaheshPujari This is not a crypto question – maybe ask it on Unix Stack Exchange. (For me, echo -n doesn't seem to remove any newline, it just doesn't append a new one.)
Apr
4
comment Asymmetric sign in public enviroment
@user2029276 Make sure to implement signing, not some kind of encryption. (And I would propose to use an existing crypto library instead of doing it yourself.)
Apr
3
comment Are there any valid, and person readable, checksums possible?
For the flame: You should not use MD5 at all, it is broken. Use a newer Hash function like SHA-2 or SHA-3 instead (maybe suitably truncated before encoding in a readable way).
Mar
31
comment Is it safe to encrypt random data using ECB mode?
@SAIPeregrinus could please you elaborate on your comment in form of a proper answer?
Mar
31
comment Is it safe to encrypt random data using ECB mode?
@ChaitanyaGupta could you put your additional information into the question (there is an "edit" link)?
Mar
19
comment Deciphering text encrypted with a changing cipher
It is not exactly CFB (for $k > 1$), as it doesn't really use blocks. But I guess the proof might be transferable (and might need a large enough $k$).
Mar
18
comment Composition of non-perfect encryption keys
Please note that composing encryption functions is usually not the same as doing some operation on their keys. Also, your meaning of key seems to be as a random variable (which has a distribution), where I would usually think of an individual key.
Mar
18
comment MAC in SSH packet encryption, benefits to not including it?
It allows an attacker to modify your data. If you are an attacker, this would be an advantage ;-) (The MAC is not there for authentication of the other end, but to make sure that an attacker doesn't modify your data.)
Mar
17
comment What practical uses can random hash collisions be put to?
Could you detail how one would use this machine (as described in the question, it is actually a random-first-preimage-machine) to sign different jar files or similar non-random data? Or do you simply want to use the machine as a RNG?
Mar
15
comment Why does consecutive permutations or consecutive substitutions not enhance security?
@fgrieu I guess this could be meant to apply to unkeyed permutations/substitutions only?
Mar
15
comment Encryption with a known plaintext
And if using a single block message (and zero key), your scheme is actually CBC-MAC, of which CMAC is a modification. (CMAC XORs the plaintext with some derived key before encrypting it.)
Mar
8
comment Can IGE mode be parallelized?
Hi, welcome to cryptography Stack Exchange. Your message was migrated here from Security Stack Exchange, because it is about a mode of operation, and better answered here. Please create an account here using the same Mail address as you used as Security SE, to be able to claim your question, possibly edit it, and accept an answer.
Mar
8
comment If a cipher has key length shorter than plaintext, then it is not perfectly secure
Perfect secrecy is not about any time bound attacker. The point is not that brute force takes some smaller number of steps, but that trying all keys gives you less than all messages with a smaller key size.
Mar
8
comment how to integrate 2-3 algorithms to encrypt large data fastly and securely insted using AES?
What is your actual question here?