Oct 22, 2015 PBKDF2 HMAC SHA256 module in C. The C module contains a wrapper for OpenSSL's PBKDF2 implementation, and a simple salt generator. PBKDF2 (Password-Based Key Derivation Function #2), defined in PKCS #5, is an algorithm for deriving a random value from a.
PBKDF2 HMAC SHA256 module in C
Background
The C module contains a wrapper for OpenSSL's PBKDF2 implementation, and a simple salt generator.
PBKDF2 (Password-Based Key Derivation Function #2), defined in PKCS #5, is an algorithm for deriving a random value from a password.
Openssl rsa_generate_key_ex example. RSAgeneratekeyex generates a key pair and stores it in the RSA structure provided in rsa. The pseudo-random number generator must be seeded prior to calling RSAgeneratekeyex. The modulus size will be of length bits, and the public exponent will be e. Key sizes with num should be considered insecure.
The algorithms applies a pseudo-random function -- SHA256 HMAC in this case -- to the password along with a salt string and repeats the process multiple times to create a derived key (i.e., a hash). The derived key can be stored -- along with the plain-text salt string -- to, for example, a password file or database table.
Hmac Sha256 Key Generator Java Key
Using a salt along with the password reduces the ability to use rainbow tables to crack the hash. Increasing the number of iterations makes it harder to crack the password using brute force methods but it slows down the key derivation too.
More information:
Usage
See test.c for a sample program.
Basically, function hash_password returns a digest string that can be stored to persistent storage. The string has the format of
where [digest] is pbkdf2-sha256([salt], [password], iter=PBKDF2_ITERATIONS).
JSON Web Tokens (JWT) can be integrityprotected with a hash-based message authenticationcode(HMAC). The producer and consumer must posses a shared secret, negotiatedthrough some out-of-band mechanism before the JWS-protected object iscommunicated (unless the producer secures the JWS object for itself).
The Nimbus JOSE+JWT library supports all standardJWS algorithms for HMAC protection (note the minimum secret lengthrequirement):
- HS256 - HMAC with SHA-256, requires 256+ bit secret
- HS384 - HMAC with SHA-384, requires 384+ bit secret
- HS512 - HMAC with SHA-512, requires 512+ bit secret
The JWT includes a set of claimsor assertions, packaged in a JSON object. Note that the SignedJWT.verifymethod only checks the validity of the HMAC. The claims, which treatment isapplication specific, must therefore be subsequently checked by yourapplication code.
Hmac Sha256 Generator
Example code: