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BN_RECP_CTX_new (3)
  • >> BN_RECP_CTX_new (3) ( Разные man: Библиотечные вызовы )
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    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

    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 structure. BN_RECP_CTX_init() initializes an existing uninitialized 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 itself.

    BN_RECP_CTX_set() 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.

    BN_div_recp() 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

    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 values.

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

    SEE ALSO

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

    HISTORY

    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.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    SEE ALSO
    HISTORY


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