RSA(3)                                                     RSA(3)

     NAME
          asn1dump, asn1toRSApriv, decodepem, decodepemchain,
          rsadecrypt, rsaencrypt, rsafill,, rsagen, rsaprivalloc,
          rsaprivfree, rsaprivtopub, rsapuballoc, rsapubfree,
          X509toRSApub, X509dump, X509gen, X509req, 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)

          RSApriv*  rsafill(mpint *n, mpint *ek, mpint *dk, 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)

          void      asn1dump(uchar *der, int len)

          uchar*    decodepem(char *s, char *type, int *len)

          PEMChain* decodepemchain(char *s, char *type)

          void      X509dump(uchar *cert, int ncert)

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

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

     RSA(3)                                                     RSA(3)

          char* X509verify(uchar *cert, int ncert, 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
                    {
                    RSApubpub;
                    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.

          Rsafill takes as input the bare minimum pieces of an RSA
          private key and computes the rest (kp, kq, and c2).  It
          returns a new private key.  All the mpints in the key, even
          the ones that correspond directly to rsafill's input parame-
          ters, are freshly allocated,

          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

     RSA(3)                                                     RSA(3)

          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.

          X509dump prints an X.509 certificate to standard ouptut.

          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 (see
          getfields(3)).

          X509req creates an X.509 certification request.

          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 the decoded section
          and sets *len to its decoded length.  If not, it returns
          nil, and *len is undefined.

          Decodepemchain is similar but expects a sequence of PEM-
          formatted sections and returns a linked list of the decod-
          ings:

               typedef struct PEMChain PEMChain
               struct PEMChain
               {
                         PEMChain *next;
                         uchar *pem;
                         int pemlen;
               };

     SOURCE
          /src/libsec

     SEE ALSO
          mp(3), aes(3), blowfish(3), des(3), dsa(3), elgamal(3),
          rc4(3), sechash(3), prime(3), rand(3)