Problem - Kevin Tafuro

Solution
Remove all elements of the structure except for n and e.
Discussion
OpenSSLlumps the private key and the public key into a single RSA structure. They
do this because the information in the public key is useful to anyone with the private
key. If an entity needs only the public key, you’re supposed to clear out the rest of
the data.
#include
void remove_private_key(RSA *r) {
r->d = r->p = r->q = r->dmp1 = r->dmq1 = r->iqmp = 0;
}
Be sure to deallocate the BIGNUM objects if you’re erasing the last reference to them.
Any party that has the private key should also hold on to the public key.
7.8 Converting Binary Strings to Integers for
Use with RSA
Problem
You need to encode a string as a number for use with the RSA encryption algorithm.
Solution
Use the standard PKCS #1 method for converting a nonnegative integer to a string of
a specified length. PKCS #1 is the RSA Security standard for encryption with the
RSA encryption algorithm. *
Discussion
The PKCS #1 method for representing binary strings as integers is simple. You simply
treat the binary representation of the string directly as the binary representation
of the number, where the string is considered a list of bytes from most significant to
least significant (big-endian notation).
For example, if you have the binary string “Test”, you would have a number represented
as a list of ASCII values. In decimal, these values are:
84, 101, 115, 116
* For the PKCS #1 specification, see http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/.
330 | Chapter 7: Public Key Cryptography
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.