Public Key encryption

[Timo Schulz]

On Thu Jun 13 2002; 15:52, Rüdiger Sonderfeld wrote:

> but I don't know! The gcry_pk_encrypt function don't accept unsigned char* 
> (only GCRY_SEXP).
> 
> What to do?

You can see an example how to do this in gnupg-1.1.2 g10/encode.c
I'll try to give you a basic example:

code snippets:
    if( algo == GCRY_PK_ELG || algo == GCRY_PK_ELG_E ) {
        rc = gcry_sexp_build ( &s_pkey, NULL,
                              "(public-key(elg(p%m)(g%m)(y%m)))",
                                  pkey[0], pkey[1], pkey[2] );
    }
    /* put the data into a simple list */
    if ( gcry_sexp_build( &s_data, NULL, "%m", data ) )
        BUG ();

    /* pass it to libgcrypt */
    rc = gcry_pk_encrypt( &s_ciph, s_data, s_pkey );
    gcry_sexp_release( s_data );
    gcry_sexp_release( s_pkey );

    /* extract the MPI values */        
    GCRY_SEXP list = gcry_sexp_find_token( s_ciph, "a" , 0 );
    assert( list );
    resarr[0] = gcry_sexp_nth_mpi( list, 1, 0 );
    assert( resarr[0] );
    gcry_sexp_release ( list );

    list = gcry_sexp_find_token( s_ciph, "b" , 0 );
    assert( list );
    resarr[1] = gcry_sexp_nth_mpi( list, 1, 0 );
    assert( resarr[1] );
    gcry_sexp_release ( list );

I know it seems to be a little complicated but when you work some
time with it, it's pretty easy ;-).


        Timo