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bio website codingrobots.com
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age 31
visits member for 3 years, 3 months
seen Aug 10 at 10:54
Programmer and founder at Coding Robots

Sep
24
awarded  Autobiographer
Jul
17
awarded  Announcer
May
2
comment A single password manager vs password generator/hash
@AdamSmith It is assumed that salt is a public value: usually password generators use site address for it, e.g. PBKDF2("master password", "google.com"). If the salt is secret (let's call it a "secret seed", because salt is reserved for a different term) and has enough entropy (e.g. 128 bits), then it's infeasible to guess the master password. However, this is not the scheme discussed here (deriving many passwords from a single one), as the user has to remember a random value along with the master password for it to work.
Apr
29
comment A single password manager vs password generator/hash
@AdamSmith the difference between bruteforcing/running dictionary attack on encrypted password database and a hash of the generated password is only in the cost of the hash operation. E.g. if password database is encrypted with a key derived with PBKDF2-HMAC-SHA256 with 100,000 iterations and the password generator generates passwords by running 100,000 iterations of PBKDF2-HMAC-SHA256, and a website that leaked passwords uses bcrypt to hash passwords, then guessing the master password for password generator (bcrypt(PBKDF2-SHA256(master_password))) is only harder for the cost of bcrypt.
Oct
16
awarded  Excavator
Oct
16
revised Examples of applications that use the Schnorr digital signature?
OpenSSL -> OpenSSH
Oct
15
suggested suggested edit on Examples of applications that use the Schnorr digital signature?
Aug
3
awarded  Yearling
Apr
25
revised Tamper-proofing log files
Fixed link
Apr
25
suggested suggested edit on Tamper-proofing log files
Mar
31
comment Single-purpose symmetric encryption scheme for single files
@StephenTouset no, it uses MD5. See github.com/Chronic-Dev/openssl/blob/master/apps/enc.c#L552 and openssl.org/docs/crypto/… or stackoverflow.com/questions/9488919/openssl-password-to-key. Also, the output format doesn't seem to be documented.
Mar
30
comment Single-purpose symmetric encryption scheme for single files
Have you seen the file format of scrypt utility? It's a good reference on how to do it properly: code.google.com/p/scrypt/source/browse/trunk/FORMAT
Mar
30
comment Single-purpose symmetric encryption scheme for single files
@StephenTouset proper key derivation?
Mar
13
comment Security of tokenization of plain text conversations - cryptanalysis
See also crypto.stackexchange.com/questions/3645/…
Mar
9
comment ChaCha cipher + Poly1305
I think you're referring to hashing the result of DH. djb says you should hash the result of curve25519 scalar multiplication before using it ("Both of you can then hash this shared secret and use the result as a key for, e.g., Poly1305-AES." cr.yp.to/ecdh.html), so crypto_box uses HSalsa as a hash function for shared key. Crypto_secretbox doesn't have this step.
Mar
8
comment ChaCha cipher + Poly1305
HSalsa is used to turn Salsa20 (8-byte nonce) into XSalsa20 (24-byte nonce) as per "Extending the Salsa20 nonce" paper: cr.yp.to/snuffle/xsalsa-20081128.pdf
Jan
26
revised Using UMAC with stream cypher
added 139 characters in body
Jan
26
answered Using UMAC with stream cypher
Jan
26
revised Hashing passwords with a salt - why use different salt for everyone?
s/getting/building/
Jan
26
revised Hashing passwords with a salt - why use different salt for everyone?
Rephrase the whole answer