MirBSD manpage: BN_div_recp(3), BN_mod_mul_reciprocal(3), BN_RECP_CTX_free(3), BN_RECP_CTX_init(3), BN_RECP_CTX_new(3), BN_RECP_CTX_set(3)



     BN_mod_mul_reciprocal,  BN_div_recp, BN_RECP_CTX_new,
     BN_RECP_CTX_init, BN_RECP_CTX_free, BN_RECP_CTX_set - modu-
     lar multiplication using reciprocal


      #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);


     BN_mod_mul_reciprocal() can be used to perform an efficient
     BN_mod_mul(3) 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.

     BN_RECP_CTX_new() allocates and initializes a BN_RECP struc-
     ture. BN_RECP_CTX_init() initializes an existing uninitial-
     ized BN_RECP.

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

     BN_RECP_CTX_set() stores m in recp and sets it up for com-
     puting 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.

     BN_div_recp() divides a by m using recp. It places the quo-
     tient in dv and the remainder in rem.

     The BN_RECP_CTX structure is defined as follows:

MirBSD #10-current         2005-02-05                           1


      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.


     BN_RECP_CTX_new() returns the newly allocated BN_RECP_CTX,
     and NULL on error.

     BN_RECP_CTX_init() and BN_RECP_CTX_free() have no return

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


     bn(3), ERR_get_error(3), BN_add(3), BN_CTX_new(3)


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

MirBSD #10-current         2005-02-05                           2

Generated on 2022-12-24 01:00:14 by $MirOS: src/scripts/roff2htm,v 1.113 2022/12/21 23:14:31 tg Exp $ — This product includes material provided by mirabilos.

These manual pages and other documentation are copyrighted by their respective writers; their sources are available at the project’s CVSweb, AnonCVS and other mirrors. The rest is Copyright © 2002–2022 MirBSD.

This manual page’s HTML representation is supposed to be valid XHTML/1.1; if not, please send a bug report — diffs preferred.

Kontakt / Impressum & Datenschutzerklärung