+ (NSString*)sha256HashFor:(NSString*)input{
constchar *str = [input UTF8String];
unsigned char result[CC_SHA256_DIGEST_LENGTH];
CC_SHA256(str, (CC_LONG)strlen(str), result);
NSMutableString *ret = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH*2];
for(int i = 0; i<CC_SHA256_DIGEST_LENGTH; i++) {
[ret appendFormat:@"%02x",result[i]];
}
return ret;
}
