ref: fff474d8639fd387aac437e0a84a06604000c3ba
dir: /sys/man/2/elgamal/
.TH ELGAMAL 2 .SH NAME eggen, egencrypt, egdecrypt, egsign, egverify, egpuballoc, egpubfree, egprivalloc, egprivfree, egsigalloc, egsigfree, egprivtopub - elgamal encryption .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .br .B #include <mp.h> .br .B #include <libsec.h> .PP .B EGpriv* eggen(int nlen, int nrep) .PP .B mpint* egencrypt(EGpub *k, mpint *in, mpint *out) .PP .B mpint* egdecrypt(EGpriv *k, mpint *in, mpint *out) .PP .B EGsig* egsign(EGpriv *k, mpint *m) .PP .B int egverify(EGpub *k, EGsig *sig, mpint *m) .PP .B EGpub* egpuballoc(void) .PP .B void egpubfree(EGpub*) .PP .B EGpriv* egprivalloc(void) .PP .B void egprivfree(EGpriv*) .PP .B EGsig* egsigalloc(void) .PP .B void egsigfree(EGsig*) .PP .B EGpub* egprivtopub(EGpriv*) .SH DESCRIPTION .PP Elgamal is a public key encryption and signature algorithm. The owner of a key publishes the public part of the key: .EX struct EGpub { mpint *p; // modulus mpint *alpha; // generator mpint *key; // (encryption key) alpha**secret mod p }; .EE This part can be used for encrypting data (with .IR egencrypt ) to be sent to the owner. The owner decrypts (with .IR egdecrypt ) using his private key: .EX struct EGpriv { EGpub pub; mpint *secret; // (decryption key) }; .EE .PP Keys are generated using .IR eggen . .I 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. .I Egprivtopub returns a newly allocated copy of the public key corresponding to the private key. .PP The routines .IR egpuballoc , .IR egpubfree , .IR egprivalloc , and .I egprivfree are provided to manage key storage. .PP .I Egsign signs message .I m using a private key .I k yielding a .EX struct EGsig { mpint *r, *s; }; .EE .I Egverify returns 0 if the signature is valid and \-1 if not. .PP The routines .I egsigalloc and .I egsigfree are provided to manage signature storage. .SH SOURCE .B /sys/src/libsec .SH SEE ALSO .IR mp (2), .IR aes (2), .IR blowfish (2), .IR des (2), .IR dsa (2), .IR rc4 (2), .IR rsa (2), .IR sechash (2), .IR prime (2), .IR rand (2)