BN_BLINDING_new 3 2008-05-09 0.9.9-dev OpenSSL

### NAME

BN_BLINDING_new, BN_BLINDING_free, BN_BLINDING_update, BN_BLINDING_convert, BN_BLINDING_invert, BN_BLINDING_convert_ex, BN_BLINDING_invert_ex, BN_BLINDING_set_thread, BN_BLINDING_cmp_thread, BN_BLINDING_get_flags, BN_BLINDING_set_flags, BN_BLINDING_create_param - blinding related BIGNUM functions.

### LIBRARY

libcrypto, -lcrypto

### SYNOPSIS

     #include

     BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai,
            BIGNUM *mod);
     void BN_BLINDING_free(BN_BLINDING *b);
     int BN_BLINDING_update(BN_BLINDING *b,BN_CTX *ctx);
     int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx);
     int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx);
     int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b,
            BN_CTX *ctx);
     int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
            BN_CTX *ctx);

     void BN_BLINDING_set_thread(BN_BLINDING *);
     int BN_BLINDING_cmp_thread(const BN_BLINDING *,
            const CRYPTO_THREADID *);
     unsigned long BN_BLINDING_get_flags(const BN_BLINDING *);
     void BN_BLINDING_set_flags(BN_BLINDING *, unsigned long);
     BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
            const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
            int (*bn_mod_exp)(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
                              const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx),
            BN_MONT_CTX *m_ctx);

### DESCRIPTION

BN_BLINDING_new() allocates a new BN_BLINDING structure and copies the A and Ai values into the newly created BN_BLINDING object.

BN_BLINDING_free() frees the BN_BLINDING structure.

BN_BLINDING_update() updates the BN_BLINDING parameters by squaring the A and Ai or, after specific number of uses and if the necessary parameters are set, by re-creating the blinding parameters.

BN_BLINDING_convert_ex() multiplies n with the blinding factor A. If r is not NULL a copy the inverse blinding factor Ai will be returned in r (this is useful if a RSA object is shared amoung several threads). BN_BLINDING_invert_ex() multiplies n with the inverse blinding factor Ai. If r is not NULL it will be used as the inverse blinding.

BN_BLINDING_convert() and BN_BLINDING_invert() are wrapper functions for BN_BLINDING_convert_ex() and BN_BLINDING_invert_ex() with r set to NULL.

BN_BLINDING_set_thread() and BN_BLINDING_cmp_thread() set and compare the "thread id" of the BN_BLINDING structure, allowing users of the BN_BLINDING structure to provide proper locking if needed for multi-threaded use.

BN_BLINDING_get_flags() returns the BN_BLINDING flags. Currently there are two supported flags: BN_BLINDING_NO_UPDATE and BN_BLINDING_NO_RECREATE. BN_BLINDING_NO_UPDATE inhibits the automatic update of the BN_BLINDING parameters after each use and BN_BLINDING_NO_RECREATE inhibits the automatic re-creation of the BN_BLINDING parameters after a fixed number of uses (currently 32). In newly allocated BN_BLINDING objects no flags are set. BN_BLINDING_set_flags() sets the BN_BLINDING parameters flags.

BN_BLINDING_create_param() creates new BN_BLINDING parameters using the exponent e and the modulus m. bn_mod_exp and m_ctx can be used to pass special functions for exponentiation (normally BN_mod_exp_mont() and BN_MONT_CTX).

### RETURN VALUES

BN_BLINDING_new() returns the newly allocated BN_BLINDING structure or NULL in case of an error.

BN_BLINDING_update(), BN_BLINDING_convert(), BN_BLINDING_invert(), BN_BLINDING_convert_ex() and BN_BLINDING_invert_ex() return 1 on success and 0 if an error occured.

BN_BLINDING_get_thread_id() returns the thread id (a unsigned long value) or 0 if not set. BN_BLINDING_cmp_thread() returns 0 if the thread id associated with the BN_BLINDING structure equals the provided thread id (which can be obtained by CRYPTO_THREADID_set()), otherwise it returns -1 or +1 to indicate the thread ids are different (if the target architecture supports ordering of thread ids, this follows the traditional "cmp" semantics of memcmp() or strcmp()).

BN_BLINDING_get_flags() returns the currently set BN_BLINDING flags (a unsigned long value).

BN_BLINDING_create_param() returns the newly created BN_BLINDING parameters or NULL on error.

### SEE ALSO

openssl_bn(3)

### HISTORY

BN_BLINDING_convert_ex, BN_BLINDIND_invert_ex, BN_BLINDING_get_thread_id, BN_BLINDING_set_thread_id, BN_BLINDING_set_flags, BN_BLINDING_get_flags and BN_BLINDING_create_param were first introduced in OpenSSL 0.9.8

BN_BLINDING_get_thread_idptr, BN_BLINDING_set_thread_idptr were first introduced in OpenSSL 0.9.9

BN_BLINDING_get_thread_id, BN_BLINDING_set_thread_id, BN_BLINDING_get_thread_idptr, BN_BLINDING_set_thread_idptr were all deprecated in favour of BN_BLINDING_set_thread, BN_BLINDING_cmp_thread which were introduced in OpenSSL 0.9.9

### AUTHOR

Nils Larsch for the OpenSSL project (http://www.openssl.org).