iOS RC4加解密算法

-(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];

}