ELGAMAL(3)ELGAMAL(3)

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)
int         egverify(EGpub *k, EGsig *sig, mpint *m)
EGpub*       egpuballoc(void)
void        egpubfree(EGpub*)
EGpriv*      egprivalloc(void)
void        egprivfree(EGpriv*)
EGsig*       egsigalloc(void)
void        egsigfree(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
{
EGpub pub;
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
/home/opt/plan9port/src/libsec

SEE ALSO
mp(3), aes(3), blowfish(3), des(3), dsa(3), rc4(3), rsa(3), sechash(3), prime(3), rand(3)

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