(MFC) Hashing Encoded Data

This example explains how it's important to know exactly what bytes are getting hashed when working with encoded data, such as hex, base64, etc.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkCrypt2.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkCrypt2 crypt;

    // Imagine we want to SHA-1 hash this A9133F6DC63E85BE0619763F8975CA076FF91B95CB6F121CD21C016143315E11B9ED4374F174B2CC
    const char *strToHash = "A9133F6DC63E85BE0619763F8975CA076FF91B95CB6F121CD21C016143315E11B9ED4374F174B2CC";

    // The question is:  Do we want to hash the bytes 0xA9, 0x13, 0x3F...
    // or do we want to literally hash each us-ascii byte:  'A', '9', '1', '3'.

    // The results will obviously be different depending on what bytes are actually hashed.

    // To hash the decoded bytes (i.e. 0xA9, 0x13, 0x3F...) we do this:

    // "hex" is not an actual character encoding.  It's a special value to be used to tell Chilkat to hex decode
    // the string and pass the decoded bytes to the hash algorithm...
    crypt.put_Charset("hex");
    crypt.put_HashAlgorithm("sha1");
    // Get the hash result in lowercase hex
    crypt.put_EncodingMode("hex_lower");
    const char *hashValue = crypt.hashStringENC(strToHash);
    strOut.append("hash of decoded hex bytes: ");
    strOut.append(hashValue);
    strOut.append("\r\n");

    // The result is 7a4a2ba73811fab98b4baaee2df164cbdd0d8e8e

    // This is how to hash the us-ascii byte values:
    // The Charset property defines the byte representation of the string passed to the hash algorithm:
    crypt.put_Charset("us-ascii");
    // The EncodingMode property defines the binary encoding (hex, base64, etc.) of the hash returned as an encoded string.
    crypt.put_EncodingMode("hex");
    crypt.put_HashAlgorithm("sha1");

    hashValue = crypt.hashStringENC(strToHash);
    strOut.append("hash of us-ascii bytes: ");
    strOut.append(hashValue);
    strOut.append("\r\n");

    // The result is:  2A7500F88734F4B19C79852CA0FF3E1C561F31C8

    // 


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }