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BN_BLINDING_NEW(3) Library Functions Manual BN_BLINDING_NEW(3)

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_get_thread_id, BN_BLINDING_set_thread_id, BN_BLINDING_thread_id, BN_BLINDING_get_flags, BN_BLINDING_set_flags, BN_BLINDING_create_paramblinding related BIGNUM functions

#include <openssl/bn.h>

BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod);





BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx);

BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx);


unsigned long
BN_BLINDING_get_thread_id(const BN_BLINDING *);

BN_BLINDING_set_thread_id(BN_BLINDING *, unsigned long);



unsigned long
BN_BLINDING_get_flags(const BN_BLINDING *);

BN_BLINDING_set_flags(BN_BLINDING *, unsigned long);

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);

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

() frees the BN_BLINDING structure. If b is a NULL pointer, no action occurs.

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

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

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

() provides access to the CRYPTO_THREADID object within the BN_BLINDING structure. This is to help users provide proper locking if needed for multi-threaded use. The thread ID object of a newly allocated BN_BLINDING structure is initialised to the thread ID in which BN_BLINDING_new() was called.

() 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. () sets the BN_BLINDING_* parameters flags.

() 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(3) and BN_MONT_CTX).

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 occurred.

BN_BLINDING_thread_id() returns a pointer to the thread ID object within a BN_BLINDING object.

BN_BLINDING_get_flags() returns the currently set BN_BLINDING_* flags (an unsigned long value).

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

BN_new(3), RSA_blinding_on(3)

BN_BLINDING_new(), BN_BLINDING_free(), BN_BLINDING_update(), BN_BLINDING_convert(), and BN_BLINDING_invert() first appeared in SSLeay 0.9.0 and have been available since OpenBSD 2.4.

BN_BLINDING_convert_ex(), BN_BLINDIND_invert_ex(), BN_BLINDING_get_thread_id(), BN_BLINDING_set_thread_id(), BN_BLINDING_get_flags(), BN_BLINDING_set_flags(), and BN_BLINDING_create_param() first appeared in OpenSSL 0.9.8 and have been available since OpenBSD 4.5.

BN_BLINDING_thread_id() first appeared in OpenSSL 1.0.0 and has been available since OpenBSD 4.9.

Nils Larsch <>

June 6, 2019 OpenBSD-7.3