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Alphabetical listing for B

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BN_mod_mul_reciprocal(3)
NAME
  BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_init,
  BN_RECP_CTX_free, BN_RECP_CTX_set - Modular multiplication using reciprocal

SYNOPSIS
  #include <openssl/bn.h>

  BN_RECP_CTX *BN_RECP_CTX_new(
	  void );

  void BN_RECP_CTX_init(
	  BN_RECP_CTX *recp );

  void BN_RECP_CTX_free(
	  BN_RECP_CTX *recp );

  int BN_RECP_CTX_set(
	  BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx );

  int BN_div_recp(
	  BIGNUM *dv, BIGNUM *rem, BIGNUM *a, BN_RECP_CTX *recp,
  BN_CTX *ctx );

  int BN_mod_mul_reciprocal(
	  BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_RECP_CTX *recp, BN_CTX *ctx );

DESCRIPTION
  The BN_mod_mul_reciprocal() function can be used to perform an efficient
  BN_mod_mul() operation when the operation will be performed repeatedly with
  the same modulus. It computes r=(a*b)%m using recp=1/m, which is set as
  described below.  ctx is a previously allocated BN_CTX used for temporary
  variables.

  The BN_RECP_CTX_new() function allocates and initializes a BN_RECP
  structure. The BN_RECP_CTX_init() function initializes an existing
  uninitialized BN_RECP.

  The BN_RECP_CTX_free() function frees the components of the BN_RECP, and,
  if it was created by BN_RECP_CTX_new(), also the structure itself.

  The BN_RECP_CTX_set() function stores m in recp and sets it up for
  computing 1/m and shifting it left by BN_num_bits(m)+1 to make it an
  integer. The result and the number of bits it was shifted left will later
  be stored in recp.

  The BN_div_recp() function divides a by m using recp. It places the
  quotient in dv and the remainder in rem.

  The BN_RECP_CTX structure is defined as follows:

	typedef struct bn_recp_ctx_st
	       {
	       BIGNUM N;       /* the divisor */
	       BIGNUM Nr;      /* the reciprocal */
	       int num_bits;
	       int shift;
	       int flags;
	       } BN_RECP_CTX;

  It cannot be shared between threads.

RETURN VALUES
  The BN_RECP_CTX_new() function returns the newly allocated BN_RECP_CTX, and
  NULL on error.

  The BN_RECP_CTX_init() and BN_RECP_CTX_free() functions have no return
  values.

  For the other functions, 1 is returned for success, 0 on error. The error
  codes can be obtained by  ERR_get_error(3).

HISTORY
  The BN_RECP_CTX structure was added in SSLeay 0.9.0.	Before that, the
  BN_reciprocal() function was used instead, and the BN_mod_mul_reciprocal()
  arguments were different.

SEE ALSO
  Functions: bn(3), err(3), BN_add(3), BN_CTX_new(3)

Index for Section 3

Alphabetical listing for B

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