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To work with MPIs, storage must be allocated and released for the numbers. This can be done with one of these functions:
Allocate a new MPI object, initialize it to 0 and initially allocate enough memory for a number of at least nbits. This pre-allocation is only a small performance issue and not actually necessary because Libgcrypt automatically re-allocates the required memory.
This is identical to gcry_mpi_new
but allocates the MPI in the so
called "secure memory" which in turn will take care that all derived
values will also be stored in this "secure memory". Use this for highly
confidential data like private key parameters.
Create a new MPI as the exact copy of a but with the constant and immutable flags cleared.
Release the MPI a and free all associated resources. Passing
NULL
is allowed and ignored. When a MPI stored in the "secure
memory" is released, that memory gets wiped out immediately.
The simplest operations are used to assign a new value to an MPI:
Assign the value of u to w and return w. If
NULL
is passed for w, a new MPI is allocated, set to the
value of u and returned.
Assign the value of u to w and return w. If
NULL
is passed for w, a new MPI is allocated, set to the
value of u and returned. This function takes an unsigned
int
as type for u and thus it is only possible to set w to
small values (usually up to the word size of the CPU).
If u is not negative and small enough to be stored in an
unsigned int
variable, store its value at w. If the
value does not fit or is negative, return GPG_ERR_ERANGE
and do not
change the value stored at w. Note that this function returns
an unsigned int
so that this value can immediately be used with
the bit test functions. This is in contrast to the other "_ui"
functions which allow for values up to an unsigned long
.
Swap the values of a and b.
Set u into w and release u. If w is
NULL
, only u will be released.
Set the sign of w to the negative of u.
Clear the sign of w.
Next: MPI formats, Previous: Data types, Up: MPI library [Contents][Index]