-(NSString *)encrypt:(NSString *)string withKey:(NSString *)key{
self.sBox = [[self frameSBox:key] mutableCopy];
unichar code[string.length];
int i = 0;
int j = 0;
for (int n = 0; n < string.length; n++) {
i = (i + 1) % SBOX_LENGTH;
j = (j + [[self.sBox objectAtIndex:i]integerValue]) % SBOX_LENGTH;
[self.sBox exchangeObjectAtIndex:i withObjectAtIndex:j];
NSInteger index=([self.sBox[i] integerValue]+[self.sBox[j] integerValue]);
NSInteger rand=([self.sBox[(index%SBOX_LENGTH)] integerValue]);
code[n]=(rand ^ (int)[string characterAtIndex:n]);
}
const unichar* buffer;
buffer = code;
return [NSString stringWithCharacters:buffer length:string.length];
}
- (NSString*) decrypt:(NSString*)string withKey:(NSString*)key
{
return [self encrypt:string withKey:key];
}
-(NSArray *)frameSBox:(NSString *)keyValue{
NSMutableArray *sBox = [[NSMutableArray alloc] initWithCapacity:SBOX_LENGTH];
int j = 0;
for (int i = 0; i < SBOX_LENGTH; i++) {
[sBox addObject:[NSNumber numberWithInteger:i]];
}
for (int i = 0; i < SBOX_LENGTH; i++) {
j = (j + [sBox[i] integerValue] + [keyValue characterAtIndex:(i % keyValue.length)]) % SBOX_LENGTH;
[sBox exchangeObjectAtIndex:i withObjectAtIndex:j];
}
return [NSArray arrayWithArray:sBox];
}
原文：http://www.cnblogs.com/vfeng/p/5125146.html