如何在iOS中实现Blowfish算法 [英] How to implement Blowfish algorithm in iOS
问题描述
在 iOS 中实施 BlowFish ECB 加密的最佳方式是什么?
我一直在谷歌搜索,并找到了图书馆这里。但是没有这个库的文档。不确定如何使用它。
What is the best way to implement BlowFish ECB encryption in iOS??? I have been googling a lot and found the library here. But there are no documentation of this library. Not sure how to use it.
推荐答案
我从 Bruce Schneier的网站。以下是加密方法的外观:
I got Paul Kocher implementation from Bruce Schneier's website. And here is how an encryption method may look like:
#define PADDING_PHRASE @" "
#import "CryptoUtilities.h"
#import "blowfish.h"
#import "NSData+Base64Utilities.h"
@implementation CryptoUtilities
+ (NSString *)blowfishEncrypt:(NSData *)messageData usingKey:(NSData *)secretKey
{
NSMutableData *dataToEncrypt = [messageData mutableCopy];
if ([dataToEncrypt length] % 8) {
NSMutableData *emptyData = [[PADDING_PHRASE dataUsingEncoding:NSUTF8StringEncoding] mutableCopy];
emptyData.length = 8 - [dataToEncrypt length] % 8;
[dataToEncrypt appendData:emptyData];
}
// Here we have data ready to encipher
BLOWFISH_CTX ctx;
Blowfish_Init (&ctx, (unsigned char*)[secretKey bytes], [secretKey length]);
NSRange aLeftRange, aRightRange;
NSData *aLeftBox, *aRightBox;
unsigned long dl = 0, dr = 0;
for (int i = 0; i < [dataToEncrypt length]; i += 8) { // Divide data into octets...
// …and then into quartets
aLeftRange = NSMakeRange(i, 4);
aRightRange = NSMakeRange(i + 4, 4);
aLeftBox = [dataToEncrypt subdataWithRange:aLeftRange];
aRightBox = [dataToEncrypt subdataWithRange:aRightRange];
// Convert bytes into unsigned long
[aLeftBox getBytes:&dl length:sizeof(unsigned long)];
[aRightBox getBytes:&dr length:sizeof(unsigned long)];
// Encipher
Blowfish_Encrypt(&ctx, &dl, &dr);
// Put bytes back
[dataToEncrypt replaceBytesInRange:aLeftRange withBytes:&dl];
[dataToEncrypt replaceBytesInRange:aRightRange withBytes:&dr];
}
return [dataToEncrypt getBase64String];
}
我不是很擅长C,但似乎我的实现工作正常。要解密你需要重复相同的步骤,但是你需要调用 Blowfish_Decrypt 而不是 Blowfish_Encrypt 。
这是一个源代码(我假设你只是解密密文,但不处理这里的填充):
I am not really good in C, but it seems that my implementation works correctly. To decrypt you need just repeat same steps, but instead of Blowfish_Encrypt you need to call Blowfish_Decrypt.
Here is a source code for that (I assume that you just decrypt the cipher text, but don't deal with padding here):
+ (NSData *)blowfishDecrypt:(NSData *)messageData usingKey:(NSData *)secretKeyData
{
NSMutableData *decryptedData = [messageData mutableCopy];
BLOWFISH_CTX ctx;
Blowfish_Init (&ctx, (unsigned char*)[secretKeyData bytes], [secretKeyData length]);
NSRange aLeftRange, aRightRange;
NSData *aLeftBox, *aRightBox;
unsigned long dl = 0, dr = 0;
for (int i = 0; i< [decryptedData length]; i += 8) { // Divide data into octets...
// …and then into quartets
aLeftRange = NSMakeRange(i, 4);
aRightRange = NSMakeRange(i + 4, 4);
aLeftBox = [decryptedData subdataWithRange:aLeftRange];
aRightBox = [decryptedData subdataWithRange:aRightRange];
// Convert bytes into unsigned long
[aLeftBox getBytes:&dl length:sizeof(unsigned long)];
[aRightBox getBytes:&dr length:sizeof(unsigned long)];
// Decipher
Blowfish_Decrypt(&ctx, &dl, &dr);
// Put bytes back
[decryptedData replaceBytesInRange:aLeftRange withBytes:&dl];
[decryptedData replaceBytesInRange:aRightRange withBytes:&dr];
}
return decryptedData;
}
您可能希望返回纯字节或Base64字符串。对于最后一种情况,我有一个类别,它添加了一个初始化器,它使用Base64字符串和一个方法初始化NSData对象,该方法允许从NSData获取Base64字符串。
You might want to return pure bytes or Base64 string. For the last case I have a category, which adds an initialiser, which initialises NSData object with Base64 string and a method, which allows to get Base64 string from NSData.
你还应该考虑使用PADDING_PHRASE,例如,如果你想要添加不仅几个空格,而是一些随机字节,该怎么办?在这种情况下,你应该以某种方式发送填充长度。
You should also think about playing with PADDING_PHRASE, for example, what if you want to add not just several spaces, but some random bytes? In this case you should send a padding length somehow.
更新:实际上,你不应该使用PADDING_PRASE你的过程。相反,你应该使用对维基百科页面的标准算法之一
Update: Actually, you should not use PADDING_PRASE in your process. Instead, you should use one of the standard algorithms for block ciphers described on Wikipedia page
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