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bio website github.com/CodesInChaos
location Frankfurt, Germany
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35m
comment Efficiently map $2^n$ unique 64-bit vectors to $2^n$ $n$-bit vectors where $n < 64$?
@Jean You can always use a standard hash function, if the number of collisions is acceptable is for you to decide.
1d
comment ECC cryptography with shorter signature when not needing high security?
@owlstead Considering that the academic ECDL record is 113 bits, a 128 curve should be acceptable for license keys. It's generally easier to crack the application, removing the key check than it is to compute that DL.
1d
comment Is this a plausible PBKDF?
@esushi? Why KBKDF? This is clearly password based, not key based.
2d
comment ECC cryptography with shorter signature when not needing high security?
The shortest usable signatures I know are BLS at twice the security level in size. You can truncate a few bits, raising the verification cost exponentially. Even if you'd use a 112 bit curve (which matches the largest academic ECDL break) this only goes down to about 90 bits.
2d
revised Is this a plausible PBKDF?
edited title
2d
comment Is this a plausible PBKDF?
Please include a compact description using mathematical notation or pseudo code instead of long c code full of unnecessary details.
Aug
20
awarded  Popular Question
Aug
20
comment Recover plaintext from truncated ciphertext using AES for FPE
Ending up with the ciphertext equaling the plaintext is not a problem. The probability for that is 1 in 10^19.
Aug
20
comment Recover plaintext from truncated ciphertext using AES for FPE
Read the Feistel network article I linked.
Aug
20
comment Recover plaintext from truncated ciphertext using AES for FPE
You might want to take a look at FFX mode which uses a pretty similar principl.
Aug
20
comment Recover plaintext from truncated ciphertext using AES for FPE
Truncation is not reversible. These truncated values are only used in the Feistel network. The feistel network ensures reversibility even when using a non reversible function.
Aug
20
comment Regular MACs vs Carter-Wegman MAC
WC style MACs need a nonce and leak the key if you ever reuse one.
Aug
20
comment Regular MACs vs Carter-Wegman MAC
AES-GCM is becoming pretty common. Salsa20/ChaChaPoly1305 are are used occasionally as well.
Aug
20
comment A patched SHA1 attempt for password verification
Unsalted SHA-1 is just as crappy a password hash as MD5.
Aug
20
comment A patched SHA1 attempt for password verification
Just send the password in plaintext (over HTTPS/SSL/TLS) to the server and use a proper password hash on the server. It's the job of TLS to protect data in transit, don't try to invent your own crappy hashing scheme instead.
Aug
19
revised How does SafeNet MobilePASS generate passwords?
deleted 32 characters in body
Aug
19
revised How do we compute IV+1 in CTR mode?
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Aug
19
revised GCM vs CTR+HMAC tradeoffs
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Aug
19
revised Difference between a nonce and IV
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Aug
19
revised How do we compute IV+1 in CTR mode?
edited tags