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Cyclist. Rubyist.


Mar
27
comment Perl DES PCBC as protection against decryption/crypt analysis
Using strong, modern encryption algorithms defeats cryptanalysis. If the algorithms we had today couldn't withstand cryptanalysis, we would replace them!
Mar
27
comment Perl DES PCBC as protection against decryption/crypt analysis
It's strong encryption that makes ciphertext difficult to turn into a plaintext. I'm not sure what advantage you think error propagation gives you.
Mar
27
comment Perl DES PCBC as protection against decryption/crypt analysis
First off, DES should be considered utterly broken for all modern purposes. The keys are trivially brute-forceable given computing power nowadays.
Mar
25
comment Is PBKDF2-HMAC-SHA1 really broken?
On the PHC mailing list, it was also realized recently that because the password in PBKDF2 takes the place of the key HMAC parameter (rather than the message), passwords also collide when they have trailing ASCII NULs on the end (ex. "password", "password\0", "password\0\0", etc.).
Mar
22
comment No of keys used in Triple DES Algorithm
I'm not sure what you mean by "security perception". One long key and three short keys (whose sum of lengths are the same as the length of the long key) are completely interchangeable.
Mar
22
answered No of keys used in Triple DES Algorithm
Mar
21
comment Entropy when iterating cryptographic hash functions
Oh, I think I understand. SHA-256 is considered a PRF. Therefore, your heuristic approach simply assumes that for all $2^{128}$ possible inputs, statistically there will still be on the order of $2^{128}$ unique prefixes.
Mar
21
comment Entropy when iterating cryptographic hash functions
Now that I've gone through the answer again (and fgrieu's question on math.se), I may be overlooking something, but where are you considering truncation? Are you, or is truncation simply a red herring here?
Mar
20
comment Entropy when iterating cryptographic hash functions
Edited. Let me know if I've messed anything up notationally.
Mar
20
revised Entropy when iterating cryptographic hash functions
added 70 characters in body
Mar
19
comment Should an AES byte key generated with OpenSSL be converted to hex?
Are you storing the key and IV in the database alongside the data being encrypted? That seems like folly. Also, if available in your version of OpenSSL, you should strongly consider using an authenticated cipher such as AES-128-GCM, which prevents tampering with ciphertexts.
Mar
19
comment Should an AES byte key generated with OpenSSL be converted to hex?
Keep in mind that while it's perfectly okay to store the key and IV as hex strings, AES as an algorithm operates on bytes and not hex strings. So you will need to reverse the process and decode from hex back to bytes before using the key and iv.
Mar
19
accepted Entropy when iterating cryptographic hash functions
Mar
18
revised Entropy when iterating cryptographic hash functions
added 5 characters in body
Mar
18
asked Entropy when iterating cryptographic hash functions
Mar
13
comment AES encryption takes more time to decrypt than encrypt
The edit doesn't seem to actually provide any information about the actual library or the encryption mode you're using.
Mar
13
comment AES encryption takes more time to decrypt than encrypt
This is going to depend extremely highly on your implementation, choice of mode, etc. There is not enough information in the question to provide an answer.
Mar
12
comment Would a symmetric cipher with a keylength a big as the data length be information theoretically secure?
To be fair, though, at the point where you have a truly random (not simply from a seeded CSPRNG), why bother with the overhead of a symmetric cipher like AES instead of simply XOR?
Mar
12
comment How is a public key actually used to encrypt something?
The details of symmetric algorithms are much more complicated than something like RSA, where encryption is "simply" exponentiation. For instance, the ChaCha20 paper describes a function (in section 2) that gets repeatedly applied to the plaintext.
Mar
6
comment Is it overkill to run a key generated by OpenSSL through pbkdf2?
This isn't an answer to the original question, but unless you have specific need for CBC, it's probably a more prudent decision to use an authenticated mode like GCM, EAX, CCM, or CCFB to prevent malicious manipulation of ciphertexts.