Hex Encoder and Decoder using Crypto++

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

Architect

United Kingdom

Member

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.

Been involved in programming from the early '80s. First on my Spectrum, then an Amstrad. Did lots of Fortran while at University before becoming involved in Forth, Prolog, Pascal, Occam, C and eventually C++. Eventually started programming on the Windows platform using Borland’s OWL framework, during my postgraduate years. When I started work in '94, I learnt MFC followed by COM and ATL and never looked back. Now working exclusively in .NET, working on WinForms, ASP.NET and the Compact Framework using C# and VB.NET. Using every bit of the .NET framework I can such as WebServices and writing my own controls for my .NET Portal, and for the Compact Framework. Still lots I don't know, but the end of the universe hasn't happened yet - I wonder if I'll have time?

I was a permanent employee for a number of companies until Dec 2000 before going independent after the DotCom I ws involved with went DotBomb. Now supplying consulting services to various institutions in London and surrounding regions i.e. UK Smile | :)

.

Now living and working in Australia, trying to be involved in the local .NET and Agile communities. Also maintaining an open source code coverage tool called PartCover whilst thinking of developing a new one.

Article Top

Poor

Excellent

Add a reason or comment to your vote: x
Votes of 3 or less require a comment

Comments and Discussions

You must Sign In to use this message board. (secure sign-in)

Search this forum
	Profile popups Noise Layout Per page

Function HexEncoder::Close not found [modified]

luozhaotian

17:16 20 Dec '08

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 Wilde

0:25 21 Dec '08

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
Sign In·View Thread·Permalink

Crypto++ Integration Article

Jeffrey Walton

18:33 8 Dec '06

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
Sign In·View Thread·Permalink

Re: Crypto++ Integration Article

Shaun Wilde

19:34 8 Dec '06

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
Sign In·View Thread·Permalink

Help me please??

xxhimanshu

23:12 4 Nov '03

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 Wilde

7:38 5 Nov '03

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
Sign In·View Thread·Permalink

we need more help

emeka

21:52 4 Feb '02

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.
Sign In·View Thread·Permalink	1.00/5 (1 vote)

Re: we need more help

SAWilde

9:21 5 Feb '02

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 Holy Handgrenade of Antioch instructions
Sign In·View Thread·Permalink	2.00/5 (1 vote)