Hex Encoder and Decoder using Crypto++

Shaun Wilde, 20 Nov 2000 CPOL views

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Encode binary data to and from hexadecimal format using the Crypto++ library

Introduction

The Crypto++ library is a freeware library of cryptographic schemes, written by Wei Dai. However the library also contains other useful classes which one is not made immediately aware of when you use the library. Two of these are the HexEncoder and HexDecoder classes which can be used to (surprise, surprise) encode and decode data to and from the hexadecimal text format e.g. 0-9,A-F.

Encoding

Encoding is very simple, say we had some data pData that was of length dwLen, that we wished to encode and store in pData2 which is of length dwLen*2, then

#include <hex.h> // from crypto++ library 
HexEncoder hexEncoder;
hexEncoder.Put(pData,dwLen);
hexEncoder.Close();
hexEncoder.Get(pData2,dwLen*2);

And there we have it. It is also possible to add multiple blocks of data to the encoders stream i.e.

HexEncoder hexEncoder;
hexEncoder.Put(pDataA,dwLenA);
hexEncoder.Put(pDataB,dwLenB);
hexEncoder.Put(pDataC,dwLenC);
hexEncoder.Close();
hexEncoder.Get(pData2,(dwLenA+dwLenB+dwLenC)*2);

Decoding

Decoding is equally simple.

HexDecoder hexDecoder;
hexDecoder.Put(pData,dwLen);
hexDecoder.Close();
hexDecoder.Get(pData2,dwLen/2);

Remarks

Thanks to Wei Dai for his permission to write this article in what is hoped to be a series of articles on the use of his Crypto++ library.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Shaun Wilde

Software Developer (Senior) MYOB
Australia

All articles are supplied as-is, as a howto on a particular task that worked for me in the past. None of the articles are supposed to be out-of-the-box freeware controls and nor should they be treated as such. Caveat emptor.

Now living and working in Australia, trying to be involved in the local .NET and Agile communities when I can.

I spend a good chunk of my spare time building OpenCover and maintaining PartCover both of which are Code Coverage utilities for .NET.

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Comments and Discussions

Function HexEncoder::Close not found [modified]

luozhaotian20-Dec-08 17:16

luozhaotian

20-Dec-08 17:16

Maybe the old version have function HexEncoder::Close. I used CryptoPP 5.5 version.I think we should use HexEncoder::MessageEnd().
The other way to use HexEncoder is to pass a CryptoPP::StringSink object to the constructor of HexEncoder:

    std::string encoded;
    CryptoPP::HexEncoder encoder( new CryptoPP::StringSink( encoded ),
        true /* Uppercase */, 2 /* Grouping */, ":" /* Separator */ );
    encoder.Put( signature, dwLen );
    encoder.MessageEnd();

Following your code and RSA sign, I created my test code. It works fine.

// HexEnDn.cpp
//

#include "stdafx.h"
#include <hex.h>
 
void display(byte * pData, size_t length)
{
	byte * pTemp = pData;
	while(length--)
	{
		std::cout << *pTemp;
		pTemp++;
	}
}
void HexTest(void)
{
	//pData
	byte pData[] = {1,2,'d','e','f','g'};
	size_t dwLen = sizeof(pData);
 
	//dump pData
	display(pData,dwLen);
	std::cout << std::endl;
 
	//Encode
	byte * pData2 = (byte *)malloc(sizeof(byte)*dwLen*2);
	CryptoPP::HexEncoder hexEncoder;
	hexEncoder.Put(pData,dwLen);
	hexEncoder.MessageEnd();
	hexEncoder.Get(pData2,dwLen*2);
 
	//dump
	display(pData2,dwLen*2);
	std::cout << std::endl;
 
	//Decode
	byte * pData3 = (byte *)malloc(sizeof(byte)*dwLen);
	CryptoPP::HexDecoder hexDecoder;
	hexDecoder.Put(pData2,dwLen*2);
	hexDecoder.Get(pData3,dwLen);
	hexDecoder.MessageEnd();
 
	//dump
	display(pData3,dwLen);
	std::cout << std::endl;
 
	//clean
	free(pData2);
	free(pData3);
}
void HexTest2(void)
{
    byte signature[] = {1,2,'d','e','f','g'};
    size_t dwLen = sizeof(signature);
    ///////////////////////////////////////
    // Signature Hex Encoding
    std::string encoded;
    CryptoPP::HexEncoder encoder( new CryptoPP::StringSink( encoded ),
        true /* Uppercase */, 2 /* Grouping */, ":" /* Separator */ );
    encoder.Put( signature, dwLen );
    encoder.MessageEnd();
 
    ///////////////////////////////////////
    // Dump
    std::cout << "Signature:" << std::endl;
    std::cout << " " << encoded << std::endl;
    std::cout << std::endl;
}
int main(int argc, char * argv[])
{
	HexTest();
	std::cout << std::endl;
	HexTest2();
	return 0;
}

The results is as follows:
defg
010264656667
defg

Signature:
01:02:64:65:66:67

modified on Sunday, December 21, 2008 12:13 AM

Re: Function HexEncoder::Close not found

Shaun Wilde21-Dec-08 0:25

Shaun Wilde

21-Dec-08 0:25

thanks for the update

I'll be more enthusiastic about encouraging thinking outside the box when there's evidence of any thinking going on inside it. - pTerry
BizSquawk

Crypto++ Integration Article

Jeffrey Walton8-Dec-06 18:33

Jeffrey Walton

8-Dec-06 18:33

Hi Shaun,

I'm not trying to steal your thunder...

http://www.codeproject.com/useritems/CryptoPPIntegration.asp[^]

If you would be so kind as to add some of your hints, it would be very appreciated.

Jeff

Re: Crypto++ Integration Article

Shaun Wilde8-Dec-06 19:34

Shaun Wilde

8-Dec-06 19:34

No worries - I haven't used Crypto++ for years, I switched from C++/MFC to C#/.NET about this time - glad someone else has taken up the banner.

I'll be more enthusiastic about encouraging thinking outside the box when there's evidence of any thinking going on inside it. - pTerry
www.many-monkeys.com

Help me please??

xxhimanshu4-Nov-03 23:12

xxhimanshu

4-Nov-03 23:12

hi all,

i am trying to use as it is the rijndael algorithm..for encrypting and decrypting the xml file...using AES rijndael..32 bit key and block size and also the method is CBC..it adds a few characters at the end of the file which makes it an invalid XML file..while using BLANKs..I am getting the valid XML file..Now i have to do is a server side encryption of the XML files..from php script..so i am using mcrypt library to do the same..but when i use this class to decrypt the same file it says can't secrypt..while i am using the same key and all..there the function is MCRYPT_RIJNDAEL_256..CBC and ECB..but nothing is working..can anyone help me out there in doing the same..or if there is any encryption which works as same in php and vc++ so that i just have to use the function and can do the same..Please help me out..any pointers and ideas are highly appreciated..
Thanks a lot in advance..
Regards,

Himanshu

Re: Help me please??

Shaun Wilde5-Nov-03 7:38

Shaun Wilde

5-Nov-03 7:38

Sorry I can't help

I don't use PHP and I haven't used the crypto++ library for a long time now as I am always using .NET at the moment.

You might be better posting this question to one of the newsgroups that cover crypto.

I am using VB on the current project

www.many-monkeys.com

we need more help

emeka4-Feb-02 21:52

emeka

4-Feb-02 21:52

i was looking forward to reading an 'article', we actually need more in depth explanations on using the crypto++ library since there is no tutorial available.

Re: we need more help

SAWilde5-Feb-02 9:21

SAWilde

5-Feb-02 9:21

alas I wanted to show more on the crypto++ library but I didn't get the time - I haven't used the library now for over a year - the current projects I am doing do not require it - sorry

there is a mailing list that you can subscribe to have a look at the crypto++ site for more details

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Hex Encoder and Decoder using Crypto++

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Hex Encoder and Decoder using Crypto++

Introduction

Encoding

Decoding

Remarks

License

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