# Tag Info

0

You can use any word list for Diceware. The reason you may not find six dice lists is that there are not enough easy words. For example, on my system the /usr/share/dict/words dictionary contains only about 100k words and if you take $6^6$ shortest, you get 8-character "words", like "mangle's", which might be difficult to remember. You can easily do that if ...

1

I know PBKDF2 is essentially "useless" against anyone with a GPU rig and I have read that bcrypt is "useless" to anyone with an FPGA setup. Neither is useless. Newer alternatives like scrypt and the eventual PHC winner make better use of the defenders' resources, but even a thousand iterations of PBKDF2 is useful, compared to doing nothing. If you ...

2

The reason Lamport's scheme is secure against a passive attacker is that even if they see $H^{n-1}(p)$ for a given $n$, the server would require the preimage of that hash, $H^{n-2}(p)$ on the next login. The active attack, in comparison, allows Trudy to find an earlier iteration than the server is expecting. That allows calculating several login hashes by ...

3

My intuition suggests that there would be no security impact if this output were truncated to 128 bits. Is this correct? My reasoning here is that salting prevents multi-target attacks, and that collisions are unimportant in the context of password verification. Correct, there is no practical security impact. The preimage security of the hash function ...

4

It is possible to reverse the birthday bound calculation. You can get an easily computable approximation using the expected number of collisions: If you had random $n$-bit salts, after $k$ values you would expect $2^{-n}\binom{k}{2}$ collisions. If the collisions are rare, they are mostly single collisions, so there are approximately \$u = ...

2

The RAR5 archive format encrypts file data using AES in CBC mode, and generates a 256-bit key using PBDKF2-HMAC-SHA256 (32768 iterations default?). If an attacker is able to view many files encrypted this way all with the same key, the attack is to recover the key from the ciphertext. This is not an easy task, even if the IV was reused. In WinRAR, the IV ...

6

XTEA is a block cipher. It requires a block cipher mode of operation to work. Together with a block cipher mode of operation you can generate something that is secure. For this you require at least an IV, as you may otherwise encrypt identical passwords (for different users) to identical values. Or, if you encrypt each character separately, the same ...

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If the password was 8-10 random characters with alphanumerics and some symbols, a lower bound estimate of the entropy would be something like 48 bits (eight random base 64 characters). Coupled with WordPress' weak 8-round MD5, that's just over 50 bits of security. Not terribly secure. A low-resource attacker like you assume could maybe crack it in a couple ...

3

A key is derived from the password using a Password Based Key Derivation Function, in this case PBKDF2: Key = PBKDF2(HMAC−SHA1, passphrase, ssid, 4096, 256) PBKDF2 in turn is described by PKCS#5. These RSA cryptographic standards in turn are made available through RFC's nowadays, in this case RFC 2898: PKCS #5: Password-Based Cryptography Specification ...

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