RSA(2) RSA(2) NAME asn1dump, asn1toRSApriv, asn1encodeRSApriv, asn1encodeRSApub, decodePEM, rsadecrypt, rsaencrypt, rsafill, rsagen, rsaprivalloc, rsaprivfree, rsaprivtopub, rsapuballoc, rsapubfree, X509toRSApub, X509rsagen, X509rsareq, X509rsaverify, X509rsaverifydigest - RSA encryption algorithm SYNOPSIS #include <u.h> #include <libc.h> #include <mp.h> #include <libsec.h> RSApriv* rsagen(int nlen, int elen, int nrep) RSApriv* rsafill(mpint *n, mpint *e, mpint *d, mpint *p, mpint *q) mpint* rsaencrypt(RSApub *k, mpint *in, mpint *out) mpint* rsadecrypt(RSApriv *k, mpint *in, mpint *out) RSApub* rsapuballoc(void) void rsapubfree(RSApub*) RSApriv* rsaprivalloc(void) void rsaprivfree(RSApriv*) RSApub* rsaprivtopub(RSApriv*) RSApub* X509toRSApub(uchar *cert, int ncert, char *name, int nname) RSApriv* asn1toRSApriv(uchar *priv, int npriv) int asn1encodeRSApriv(RSApriv *k, uchar *buf, int len) int asn1encodeRSApub(RSApub *pk, uchar *buf, int len) void asn1dump(uchar *der, int len) uchar* decodePEM(char *s, char *type, int *len, char **new_s) uchar* X509rsagen(RSApriv *priv, char *subj, ulong valid[2], int *certlen); Page 1 Plan 9 (printed 12/23/24) RSA(2) RSA(2) uchar* X509rsareq(RSApriv *priv, char *subj, int *certlen); char* X509rsaverify(uchar *cert, int ncert, RSApub *pk) char* X509rsaverifydigest(uchar *sig, int siglen, uchar *edigest, int edigestlen, RSApub *pk) DESCRIPTION RSA is a public key encryption algorithm. The owner of a key publishes the public part of the key: struct RSApub { mpint *n; /* modulus */ mpint *ek; /* exp (encryption key) */ }; This part can be used for encrypting data (with rsaencrypt) to be sent to the owner. The owner decrypts (with rsadecrypt) using his private key: struct RSApriv { RSApub pub; mpint *dk; /* exp (decryption key) */ /* precomputed crt values */ mpint *p; mpint *q; mpint *kp; /* k mod p-1 */ mpint *kq; /* k mod q-1 */ mpint *c2; /* for converting residues to number */ }; Keys are generated using rsagen. Rsagen takes both bit length of the modulus, the bit length of the public key exponent, 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. Rsagen returns a newly allocated structure containing both public and private keys. Rsafill returns a newly allocated private key by recomputing kp, kq, and c2. Rsaprivtopub returns a newly allocated copy of the public key corresponding to the private key. The routines rsaalloc, rsafree, rsapuballoc, rsapubfree, rsaprivalloc, and rsaprivfree are provided to aid in user provided key I/O. Given a binary X.509 cert, the routine X509toRSApub returns the public key and, if name is not nil, the CN part of the Distinguished Name of the certificate's Subject. (This is Page 2 Plan 9 (printed 12/23/24) RSA(2) RSA(2) conventionally a userid or a host DNS name.) No verifica- tion is done of the certificate signature; the caller should check the fingerprint, sha1(cert), against a table or check the certificate by other means. X.509 certificates are often stored in PEM format; use dec64 to convert to binary before computing the fingerprint or calling X509toRSApub. For the special case of certificates signed by a known trusted key (in a single step, without certificate chains), X509rsaverify checks the signature on cert. It returns nil if successful, else an error string. X509rsaverifydigest takes a encoded PKCS #1 signature as used in X.509 as sig[siglen] and verifies it against the expected cryptographic hash edigest[edigestlen] of the signed data; returning nil on success or an error string. X509rsagen creates a self-signed X.509 certificate, given an RSA keypair priv, a issuer/subject string subj, and the starting and ending validity dates, valid. Length of the allocated binary certificate is stored in certlen. The sub- ject line is conventionally of the form C=US ST=NJ L=07922 O=Lucent OU='Bell Labs' CN=Eric using the quoting conventions of tokenize in getfields(2). Asn1toRSApriv converts an ASN1 formatted RSA private key into the corresponding RSApriv structure. Asn1encodeRSApriv and asn1encodeRSApub export a RSApriv or RSApub structure to ASN1 format. On success, buf is filled and the encoded byte length is returned. Otherwise -1 is returned and error string is set. Asn1dump prints an ASN1 object to standard output. DecodePEM takes a zero terminated string, s, and decodes the PEM (privacy-enhanced mail) formatted section for type within it. If successful, it returns malloced storage con- taining the decoded section, which the caller must free, and sets *len to its decoded length. Otherwise nil is returned and *len is undefined. If not nil, new_s is set to the first character beyond the type section. SOURCE /sys/src/libsec SEE ALSO mp(2), aes(2), blowfish(2), des(2), dsa(2), elgamal(2), rc4(2), sechash(2), prime(2), rand(2), rsa(8) Page 3 Plan 9 (printed 12/23/24)