Problem - Kevin Tafuro

double spc_rand_cunifvariate(double mean, double arc) {
return (mean + arc * (spc_rand_real( ) - 0.5)) / SPC_PI;
}
See Also
Recipe 11.12
11.14 Getting a Random Printable ASCII String
Problem
You want to get a random printable ASCII string.
Solution
If you do not want whitespace characters, the printable ASCII characters have values
from 33 to 126, inclusive. Simply get a random number in that range for each character.
If you want to choose from a different character set (such as the base64 character
set), map each character to a specific numeric value between 0 and the number of
characters you have. Select a random number in that range, and map the number
back to the corresponding character.
Discussion
The code presented in this section returns a random ASCII string of a specified
length, where the specified length includes a terminating NULL byte. We use the printable
ASCII characters, meaning that we never output whitespace or control characters.
Assuming a good underlying infrastructure for randomness, each character should be
equally likely. However, the ease with which an attacker can guess a single random
string is related not only to the entropy in the generator, but also to the length of the
output. If you use a single character, there are only 94 possible values, and a guess
will be right with a probability of 1/94 (not having entropy can give the attacker an
even greater advantage).
As a result, your random strings should use no fewer than 10 random characters (not
including the terminating NULL byte), which gives you about 54 bits of security. For a
more conservative security margin, you should go for 15 to 20 characters.
#include
char *spc_rand_ascii(char *buf, size_t len) {
Getting a Random Printable ASCII String | 611
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