| 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
| `/usr/local/plan9/src/libsec`
SEE ALSO
| mp(3), aes(3), blowfish(3), des(3), dsa(3), rc4(3), rsa(3), sechash(3), prime(3), rand(3)