ELGAMAL(2) ELGAMAL(2)
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;
Page 1 Plan 9 (printed 12/23/24)
ELGAMAL(2) ELGAMAL(2)
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 pri-
vate 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)
Page 2 Plan 9 (printed 12/23/24)