The following functions are used to convert between an external representation of an MPI and the internal one of Libgcrypt.
Convert the external representation of an integer stored in buffer
with a length of buflen into a newly created MPI returned which
will be stored at the address of r_mpi. For certain formats the
length argument is not required and should be passed as
buflen larger than 16 MiByte will be rejected. After a
successful operation the variable nscanned receives the number of
bytes actually scanned unless nscanned was given as
NULL. format describes the format of the MPI as stored in
2-complement stored without a length header. Note that
gcry_mpi_print stores a
0 as a string of zero length.
As used by OpenPGP (only defined as unsigned). This is basically
GCRYMPI_FMT_STD with a 2 byte big endian length header.
A length header indicating a length of more than 16384 is not allowed.
As used in the Secure Shell protocol. This is
with a 4 byte big endian header.
Stored as a string with each byte of the MPI encoded as 2 hex digits. Negative numbers are prefix with a minus sign and in addition the high bit is always zero to make clear that an explicit sign ist used. When using this format, buflen must be zero.
Simple unsigned integer.
Note that all of the above formats store the integer in big-endian format (MSB first).
Convert the MPI a into an external representation described by format (see above) and store it in the provided buffer which has a usable length of at least the buflen bytes. If nwritten is not NULL, it will receive the number of bytes actually stored in buffer after a successful operation.
Convert the MPI a into an external representation described by
format (see above) and store it in a newly allocated buffer which
address will be stored in the variable buffer points to. The
number of bytes stored in this buffer will be stored in the variable
nbytes points to, unless nbytes is
Even if nbytes is zero, the function allocates at least one byte
and store a zero there. Thus with formats
GCRYMPI_FMT_USG the caller may safely set a returned length of
0 to 1 to represent a zero as a 1 byte string.
Dump the value of a in a format suitable for debugging to
Libgcrypt’s logging stream. Note that one leading space but no trailing
space or linefeed will be printed. It is okay to pass