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MD5 Hash Calculator Pocket PC 2003/Windows CE 4.x

, 17 May 2005
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A small tool for calculating a MD5 hash.

Introduction

Background: I experienced some problems with my SD memory card in my HP IPAQ 1940. My GPS program had a lot of bugs I thought. Because it couldn't handle large maps. After some testing, I figured out that 64 MB was the magic limit. The tool I used to test was MD5 Hashing.

My simple method:

  • Create a large file (100 MB) on the SD card.
  • Calculate MD5 on the PC (SD card in card reader).
  • Insert SD card into IPAQ.
  • Calculate MD5 on the IPAQ.
  • Check if same. If not decrease size by half, if the hash is the same increase the file by 50%.

This gave the result that it was something goofy around 64 MB files.

After that I checked the obvious (thanks Rob). If there are any updates on the HP website for my IPAQ. And there was. So if you are having any problems with large (>64 MB) files on your IPAQ 1940 (or other models), check for updates at the HP website. The update for 1940 can be downloaded here.

Anyway, problem found and solved. I thought you might find it useful to have a MD5 Hasher for Pocket PC, so here it is. Parts of the code is (c) RSA Data Security, Inc.

Code snippet:

  MD5_CTX m_md5;
  CString tempHash = "";

    if (md5file(m_strFile.GetBuffer(MAX_PATH), 0, &m_md5))
    {
        for (int i = 0; i < 16; i++)
        {
            char tmp[3];
            _itoa(m_md5.digest[i], tmp, 16);
            if (strlen(tmp) == 1)
            {
                tmp[1] = tmp[0];
                tmp[0] = '0';
                tmp[2] = '\0';
            }
            tempHash += tmp;
        }
    }

The result is delivered in human readable format in tempHash.

Drop me an e-mail with comments or questions. To see what I should do instead of debugging SD-cards, have a look at www.freefloat.com.

License

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

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About the Author

mwahlberg
Web Developer
Sweden Sweden
No Biography provided

Comments and Discussions

 
GeneralFile Encryption PinmemberHails24-Jul-08 4:11 
GeneralIf part of it is copyright.... PinmemberChristian Graus17-May-05 16:45 
GeneralRe: If part of it is copyright.... Pinmembermwahlberg18-May-05 2:48 
Dear MVP,
 
Here is the (c) text:
 
/*
 **********************************************************************
 ** Copyright (C) 1990, RSA Data Security, Inc. All rights reserved. **
 **                                                                  **
 ** License to copy and use this software is granted provided that   **
 ** it is identified as the "RSA Data Security, Inc. MD5 Message     **
 ** Digest Algorithm" in all material mentioning or referencing this **
 ** software or this function.                                       **
 **                                                                  **
 ** License is also granted to make and use derivative works         **
 ** provided that such works are identified as "derived from the RSA **
 ** Data Security, Inc. MD5 Message Digest Algorithm" in all         **
 ** material mentioning or referencing the derived work.             **
 **                                                                  **
 ** RSA Data Security, Inc. makes no representations concerning      **
 ** either the merchantability of this software or the suitability   **
 ** of this software for any particular purpose.  It is provided "as **
 ** is" without express or implied warranty of any kind.             **
 **                                                                  **
 ** These notices must be retained in any copies of any part of this **
 ** documentation and/or software.                                   **
 **********************************************************************
 */
 

As you can see RSA is granting a license to use the code as long as one identifies that the works is derived from RSA's work.
GeneralMD5 is not safe now. Pinmemberokam17-May-05 15:59 
GeneralRe: MD5 is not safe now. Pinmembermwahlberg18-May-05 2:46 

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