Problem - Kevin Tafuro

for (b = 0; !BN_is_odd(x); b++)
BN_div_word(x, 2);
return b;
}
See Also
Recipes 7.4, 11.1, 11.2
7.6 Generating an RSA Key Pair
Problem
You want to use RSA to encrypt data, and you need to generate a public key and its
corresponding private key.
Solution
Use a cryptography library’s built-in functionality to generate an RSA key pair. Here
we’ll describe the OpenSSLAPI. If you insist on implementing RSA yourself (generally
a bad idea), see the following discussion.
Discussion
Be sure to see Recipes 7.1 and 7.2 for general-purpose guidance on
using public key cryptography.
The OpenSSLlibrary provides a function, RSA_generate_key( ), that generates a
{public key, private key} pair, which is stored in an RSA object. The signature for this
function is:
RSA *RSA_generate_key(int bits, unsigned long exp, void (*cb)(int, int, void),
void *cb_arg);
This function has the following arguments:
bits
Size of the key to be generated, in bits. This must be a multiple of 16, and at a
bare minimum it should be at least 1,024. 2,048 is a common value, and 4,096 is
used occasionally. The more bits in the number, the more secure and the slower
operations will be. We recommend 2,048 bits for general-purpose use.
exp
Fixed exponent to be used with the key pair. This value is typically 3, 17, or
65,537, and it can vary depending on the exact context in which you’re using
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