CodesInChaos

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bio website github.com/CodesInChaos
location Munich, Germany
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Apr
7
 comment How secure is this perl script to use an AES encryption on files?
At a glance I see two issues: 1) The key derivation is cheap. Use a proper salted password hash such as PBKDF2 or scrypt. 2) There is no MAC, this enables active attacks where an attacker modifies the ciphertext. These attacks are surprisingly strong. For example padding oracles can be used to convince the legitimate decrypter to leak enough information to leak the plaintext. That might not work with file encryption, but I strongly recommend using MACs.
Apr
7
 comment How fast can a wrong decryption key be detected using ECC?
Typically ECC is not used for encryption at all. It's only used to determine a symmetric key that's used with a symmetric cipher to do the actual encryption. Your question depends on the choice of the symmetric encryption scheme and on the nature of the plaintext.
Apr
7
 revised “Weaknesses” in SHA-256d?
added 1029 characters in body
Apr
7
 answered “Weaknesses” in SHA-256d?
Apr
6
 comment Does a trace of SSL packets provide a proof of data authenticity?
@SmitJohnth Non handshake data is authenticated with a MAC, so it's symmetric and can't be used to prove who authored that data to a third party.
Mar
27
 comment How to choose between AES-CCM and AES-GCM for storage volume encryption
GCM might be a bit faster(depends on CPU), but I don't like it. It feels very fragile.
Mar
26
 comment AES ENCRYPTION ALGORITHM
Why are you asking the same question twice?
Mar
26
 answered which asymmetric cipher provide highest performance?
Mar
26
 comment which asymmetric cipher provide highest performance?
@rsa RSA is fast for encryption but really slow for decryption. You're comparing different security levels and you're not looking at a good ECC implementation.
Mar
26
 reviewed Approve suggested edit on What is the probability of breaking the AES algorithm?
Mar
24
 reviewed Approve suggested edit on Export from US of crypto software with key-size > 56 bits still needs permission?
Mar
23
 comment Can SRP be used with Elliptic Curves?
It's certainly possible to use a protocol that generates a private key from a password hash with ECC. But the proof that the client possesses the key will be different.
Mar
23
 revised How to efficiently generate a stream of independent, but biased random bits?
added 50 characters in body
Mar
23
 reviewed Approve suggested edit on reduces the coefficients of a modulo 3 on NTRU
Mar
21
 comment RSA Certificate Owner and Issuer line meanings?
Look for X500 and X.509
Mar
20
 comment Security of Deterministic Encryption Scheme
Pretty much the only inherent issue with deterministic encryption is that it leaks if two inputs are identical. So if you apply it to individual words, security will suck. If you apply it to complete and complex files, you'll probably be OK.
Mar
20
 comment Sensible usecase for restricting special characters in passwords?
Some keyboards lack some characters, and outside ASCII you'll need to be careful about encoding.
Mar
20
 comment Even passwords are vulnerable to hash collision attacks?
The adversary can inject material (though the salt might block any collision attack). But such a collision attack at best(from his point of view) allows the attacker to create an account for which he knows two different passwords. Not very useful...
Mar
20
 comment How does the rand() function in C work?
Even when eyeballing the plot of rand() it often exhibits total failure
Mar
20
 comment How does the rand() function in C work?
Given the typical implementation of rand(), you're using a quite generous definition of "works". IMO it does not work, even for non security related stuff.
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