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

#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*)


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.


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