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age 44
visits member for 2 years, 11 months
seen 13 hours ago
programs in C and Perl, mostly

Jul
4
comment Cryptool - DES (ECB and CBC ) - double encyption
What IV did you use in CBC mode?
Apr
25
awarded  Nice Answer
Apr
23
comment Are the MD5 constants an S-Box?
More original than AES was the use of S-boxes in DES. But the term predates even that, I think.
Apr
19
awarded  Revival
Mar
16
answered Cipher Feedback Mode
Mar
16
answered Question on RSA trapdoor permutation
Mar
8
answered Number of possible keys in a Play fair cipher
Mar
5
answered How to decrypt 3DES in ECB mode (using a wordlist)?
Mar
2
comment File Encryption (EFS method)
And, as an afterthought, DPAPI has a mechanism to avoid re-encryption of secrets (like RSA private keys) protected by it, when a user changes its password. This is an added benefit.
Mar
1
comment File Encryption (EFS method)
DPAPI has several purposes in Windows besides encrypting the RSA private key (to encrypt other secrets like WiFi passwords, and IE account passwords etc.); moreover the hash from the password is used only after thousands of iterations (and a random salt) provided by the DPAPI API. This slows down direct cracking attacks on the encrypted secret key, if the NTHash is not available, e.g.
Feb
22
answered How is LUKS dm-crypt secure if the key is stored with the encrypted data?
Dec
15
answered OpenSSL PBKDF2 documentation
Dec
11
comment RC2, RC4, RC5 key length
RC2 does have a single bit resolution: it is possible to have a key of length 8 bytes (64 bits) and an effective key length (as it is called in the specification) of 42 bits, say. The RFC has some test vectors for such cases.
Dec
11
comment AES column mixing and S-Box confusion
@figlesquidge Well, the S-box is defined in terms of the field operation ($\frac{1}{ax+b}$, for some $a,b$, defining $\frac{1}{0}$ as $0$...) But I mentioned it because I need it for the mix column anyway.
Dec
11
answered AES column mixing and S-Box confusion
Dec
10
comment How is the MD2 hash function S-table constructed from Pi?
Also note that RC2 (in RFC2268) also has a permutation supposedly based on the digits of $\pi$ in its key schedule. The final table in that RFC is also unexplained (and used in other algorithms from RSA as well). These were also never explained, AFAIK.
Dec
8
comment How is the MD2 hash function S-table constructed from Pi?
I recall having read it, it was using some RC4 like thing, updating a permutation. I don't recall where, though.
Aug
17
awarded  Yearling
Aug
13
comment Is truncating a SHA512 hash to the first 160 bits as secure as using SHA1?
Note that SHA-224 is not a simple truncated version of SHA-256: the IV is different. SHA-224 is computed like SHA-256 and then truncated, but as the IV is different, the intermediate 256 bit result of SHA-224 is totally different (in general) than the SHA-256 computation. The same goes for SHA-384 vs SHA-512.
Aug
10
answered iOS Data Protection: What is the Input of the LFSR?