RSA(2)                                                     RSA(2)

     NAME
          asn1dump, asn1toRSApub, asn1toRSApriv, decodePEM,
          rsadecrypt, rsaencrypt, rsagen, rsaprivalloc, rsaprivfree,
          rsaprivtopub, rsapuballoc, rsapubfree, RSApubtoasn1,
          X509toRSApub, X509gen, X509verify - RSA encryption algorithm

     SYNOPSIS
          #include <u.h>
          #include <libc.h>
          #include <mp.h>
          #include <libsec.h>

          RSApriv* rsagen(int nlen, int elen, int nrep)

          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)

          RSApub*  asn1toRSApub(uchar *pub, int npub)

          uchar* RSApubtoasn1(RSApub *pub, int *keylen)

          RSApriv* asn1toRSApriv(uchar *priv, int npriv)

          void     asn1dump(uchar *der, int len)

          uchar*   decodePEM(char *s, char *type, int *len, char
          **new_s)

          uchar*   X509gen(RSApriv *priv, char *subj, ulong valid[2],
          int *certlen);

          uchar*   X509req(RSApriv *priv, char *subj, int *certlen);

          char*    X509verify(uchar *cert, int ncert, RSApub *pk)

     DESCRIPTION

     RSA(2)                                                     RSA(2)

          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.
          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
          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), X509verify checks the signature on cert. It returns
          nil if successful, else an error string.

     RSA(2)                                                     RSA(2)

          X509gen 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).

          Asn1toRSApub converts an ASN1-formatted RSA public key into
          the corresponding RSApub structure.

          RSApubtoasn1 encodes an RSA public key using ASN.1 DER.  It
          returns a pointer to the encoded key; if keylen is non-nil,
          it sets *keylen to the length of the encoded key.

          Asn1toRSApriv converts an ASN1 formatted RSA private key
          into the corresponding RSApriv structure.

          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)