Problem - Kevin Tafuro

This would map to the hexadecimal value:
0x54657374
If you simply treat the hexadecimal value as a number, you’ll get the integer representation.
In base 10, the previous number would be 1415934836.
If, for some reason, you need to calculate this value manually given the ASCII values
of the integers, you would compute the following:
84×256 3 + 101×256 2 + 115×256 1 + 116×256 0
In the real world, your arbitrary-precision math library will probably have a way to
turn binary strings into numbers that is compatible with the PKCS algorithm. For
example, OpenSSL provides BN_bin2bn( ), which is discussed in Recipe 7.4.
If you need to perform this conversion yourself, make sure that your numerical representation
uses either an array of char values or an array of unsigned int values. If you
use the former, you can use the binary string directly as a number. If you use the latter,
you will have to byte-swap each word on a little-endian machine before treating
the string as a number. On a big-endian machine, you need not perform any swap.
See Also
• PKCS #1 page: http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
• Recipe 7.4
7.9 Converting Integers into Binary Strings for
Use with RSA
Problem
You have a number as a result of an RSA operation that you’d like to turn into a
binary string of a fixed length.
Solution
Use the inverse of the previous recipe, padding the start of the string with zero-bits, if
necessary, to reach the desired output length. If the number is too big, return an
error.
Discussion
In practice, you should be using a binary representation of very large integers that
stores a value as an array of values of type unsigned int or type char. If you’re using a
Converting Integers into Binary Strings for Use with RSA | 331
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