用 Objective-C 实现的 Rc4 加密算法

#import <Foundation/Foundation.h>

@interface Rc4 : NSObject

+(NSString*)HloveyRC4:(NSString*)aInput key:(NSString*)aKey;

@end

#import "Rc4.h"

@implementation Rc4

+(NSString*) HloveyRC4:(NSString*)aInput key:(NSString*)aKey {
NSMutableArray *iS = [[NSMutableArray alloc] initWithCapacity:256];
NSMutableArray *iK = [[NSMutableArray alloc] initWithCapacity:256];

for (int i= 0; i<256; i++) {
[iS addObject:[NSNumber numberWithInt:i]];
}

int j=1;

for (short i=0; i<256; i++) {

UniChar c = [aKey characterAtIndex:i%aKey.length];

[iK addObject:[NSNumber numberWithChar:c]];
}

j=0;

for (int i=0; i<255; i++) {
int is = [[iS objectAtIndex:i] intValue];
UniChar ik = (UniChar)[[iK objectAtIndex:i] charValue];

j = (j + is + ik)%256;
NSNumber *temp = [iS objectAtIndex:i];
[iS replaceObjectAtIndex:i withObject:[iS objectAtIndex:j]];
[iS replaceObjectAtIndex:j withObject:temp];

}

int i=0;
j=0;

NSString *result = aInput;

for (short x=0; x<[aInput length]; x++) {
i = (i+1)%256;

int is = [[iS objectAtIndex:i] intValue];
j = (j+is)%256;

int is_i = [[iS objectAtIndex:i] intValue];
int is_j = [[iS objectAtIndex:j] intValue];

int t = (is_i+is_j) % 256;
int iY = [[iS objectAtIndex:t] intValue];

UniChar ch = (UniChar)[aInput characterAtIndex:x];
UniChar ch_y = ch^iY;

result = [result stringByReplacingCharactersInRange:NSMakeRange(x, 1) withString:[NSString stringWithCharacters:&ch_y length:1]];
}

[iS release];
[iK release];

return result;
}

@end