Problem - Kevin Tafuro

BIGNUM bn;
void BN_init(&bn);
If you’re dynamically allocating a BIGNUM object, OpenSSLprovides a function that
allocates and initializes in one fell swoop:
BIGNUM *bn = BN_new( );
You should not use malloc( ) to allocate a BIGNUM object because you are likely to
confuse the library (it may believe that your object is unallocated).
If you would like to deallocate a BIGNUM object that was allocated using BN_new( ),
pass it to BN_free( ).
In addition, for security purposes, you may wish to zero out the memory used by a
BIGNUM object before you deallocate it. If so, pass it to BN_clear( ), which explicitly
overwrites all memory in use by a BIGNUM context. You can also zero and free in one
operation by passing the object to BIGNUM_clear_free( ).
void BN_free(BIGNUM *bn);
void BN_clear(BIGNUM *bn);
void BN_clear_free(BIGNUM *bn);
Some operations may require you to allocate BN_CTX objects. These objects are
scratch space for temporary values. You should always create BN_CTX objects dynamically
by calling BN_CTX_new( ), which will return a dynamically allocated and initialized
BN_CTX object. When you’re done with a BN_CTX object, destroy it by passing it to
BN_CTX_free( ).
BN_CTX *BN_CTX_new(void);
int BN_CTX_free(BN_CTX *c);
Assigning to BIGNUM objects
Naturally, we’ll want to assign numerical values to BIGNUM objects. The easiest way to
do this is to copy another number. OpenSSLprovides a way to allocate a new BIGNUM
object and copy a second BIGNUM object all at once:
BIGNUM *BN_dup(BIGNUM *bn_to_copy);
In addition, if you already have an allocated context, you can just call BN_copy( ),
which has the following signature:
BIGNUM *BN_copy(BIGNUM *destination_bn, BIGNUM *src_bn);
This function returns destination_bn on success.
You can assign the value 0 to a BIGNUM object with the following function:
int BN_zero(BIGNUM *bn);
You can also use BN_clear( ), which will write over the old value first.
316 | Chapter 7: Public Key Cryptography
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