extracting mpi from a S-exp crypted with RSA

flebool flebool at libero.it
Tue Apr 19 21:00:14 CEST 2005

I haven't understood correctly the model for crypted keys:
in the documentation, i've found that,if i crypt with the rsa algorythm a 
S-exp TEXT in the form:

            (flags raw)
            (value MPI))

 the crypted S-exp CRYPTED is represented as:

              (a A-MPI)))

Calling the function:
int legth=gcrypt_sexp_length(CRYPTED);
I get length=2.

i want to get the mpi (a A-MPI),(that i've understood to be the crypted text 
in MPI format) but the function

gcry_mpi_t internal_mpi = gcry_sexp_nth_mpi(CRYPTED,1,GCRYMPI_FMT_USG);


for completeness,i post the output of a 
writt= gcry_sexp_sprint ( CRYPTED , GCRYSEXP_FMT_DEFAULT , buf_test2 ,(size_t) 

(i do it only to show that it seems (at least to me) to be a good S-exp in the 
format described in the documentation)

the results are: writt=166,buf_test2[500]="\000à\004\b@Ü\004\b(7:enc-val\n 
(3:rsa\n  (1:a128:

i'm not a good coder, neither a good english writer, so sorry if i haven't 
been clear, or if i haven't understood well the documentation.

thanks in advance for any help.


PS if you prefer i can post a source of an example program.
PPS:it may take some time before i can answer your replys

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