-(NSString *)ret32bitString
{
char data[32];
for (int x=0; x <32; data[x++] = (char)(‘A‘ + (arc4random_uniform(26))));
return [[NSString alloc] initWithBytes:data length:32 encoding:NSUTF8StringEncoding];
}
原文：http://www.cnblogs.com/mengfanrong/p/5060276.html