ecc ph(g)p

Elliptic curve cryptography in PHP, similar to PGP

A simple elliptic curve public key cryptography implementation in PHP, using NIST's recommended curve P-521.

Requirements

PHP 5.1.2+ (cli), or earlier with Hash extension

GMP extension

Mcrypt extension

Commands

Technical info

Encrypt and decrypt uses the AES256 (Rijndael-256) block cipher algorithm. The encrypt process picks a random point on the curve; this point's X coordinate SHA256 hash will be the 256 bit key, and Y coodinate's SHA256 hash will be the 256 bit IV for the AES256 block cipher. The <infile> encoded with these key and IV parameters, and saved to <destfile>. The X and Y coordinates are encoded and decoded with EC-ElGamal algorithm. The result are four numbers, but we only save the two X coordinates to <destfile>.key file, because the Y coordinate can be easily calculates from X coordinate.

Sign file and verify uses the ECDSA algorithm, and the hash function is SHA512. Signing results are two numbers that will be saved to <file>.sig file. Verification checks the signature in this .sig file for <file>, and prints if the signature matches or not.

Why elliptic curve cryptography is "better" than RSA?

• Elliptic curve mathematics is more complex than RSA, but the keysize is smaller, so the calculations are faster, and waste less energy.

• The RSA keypair generation needs to generate big primes, elliptic curve keypair generation only needs random numbers.
• Elliptic curve crypt use the ElGamal algorithm that works with random numbers, so the same plaintext is encoded into a different ciphertext each time, which is more secure.