NAME

eggen, egencrypt, egdecrypt, egsign, egverify, egpuballoc, egpubfree, egprivalloc, egprivfree, egsigalloc, egsigfree, egprivtopub - elgamal encryption

SYNOPSIS

­#include <u.h>
­#include <libc.h>
­#include <mp.h>
­#include <libsec.h>

EGpriv∗eggen(int nlen, int nrep)

mpint∗egencrypt(EGpub ∗k, mpint ∗in, mpint ∗out)

mpint∗egdecrypt(EGpriv ∗k, mpint ∗in, mpint ∗out)

EGsig∗egsign(EGpriv ∗k, mpint ∗m)

integverify(EGpub ∗k, EGsig ∗sig, mpint ∗m)

EGpub∗egpuballoc(void)

voidegpubfree(EGpub∗)

EGpriv∗egprivalloc(void)

voidegprivfree(EGpriv∗)

EGsig∗egsigalloc(void)

voidegsigfree(EGsig∗)

EGpub∗egprivtopub(EGpriv∗)

DESCRIPTION

Elgamal is a public key encryption and signature algorithm.  The owner of a key publishes the public part of the key:

struct EGpub
{
mpint∗p;// modulus
mpint∗alpha;// generator
mpint∗key;// (encryption key) alpha∗∗secret mod p
};

This part can be used for encrypting data (with egencrypt) to be sent to the owner. The owner decrypts (with egdecrypt) using his private key:

struct EGpriv
{
EGpubpub;
mpint∗secret; // (decryption key)
};

Keys are generated using eggen. ­Eggen takes both bit length of the modulus and the number of repetitions of the Miller-Rabin primality test to run.  If the latter is 0, it does the default number of rounds.  ­Egprivtopub returns a newly allocated copy of the public key corresponding to the private key. 

The routines egpuballoc, egpubfree, egprivalloc, and ­egprivfree are provided to manage key storage. 

­Egsign signs message ­m using a private key ­k yielding a

struct EGsig
{
mpint∗r, ∗s;
};

­Egverify returns 0 if the signature is valid and −1 if not. 

The routines ­egsigalloc and ­egsigfree are provided to manage signature storage. 

SOURCE

­/sys/src/libsec

SEE ALSO

mp(2), aes(2), blowfish(2), des(2), dsa(2), rc4(2), rsa(2), sechash(2), prime(2), rand(2)

Plan 9  —  July 25, 2002