(MFC) JWE with DEFLATE Compression

Demonstrates how to DEFLATE ("zip") compress the JWE payload prior to encryption.

Note: This example requires Chilkat v9.5.0.66 or greater.

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

See Also: Using MFC CString in Chilkat

#include <CkStringBuilder.h>
#include <CkJwe.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    // Note: This example requires Chilkat v9.5.0.66 or greater.

    bool success;
    // Create some plaintext to be encrypted.
    // This example will demonstrate with and without DEFLATE (zip) compression.
    CkStringBuilder sbPlainText;
    bool bCrLf = true;
    const char *line = "Live long and prosper.";
    sbPlainText.AppendLine(line,bCrLf);
    sbPlainText.AppendLine(line,bCrLf);
    sbPlainText.AppendLine(line,bCrLf);
    sbPlainText.AppendLine(line,bCrLf);

    // The text to be encrypted:
    strOut.append(sbPlainText.getAsString());
    strOut.append("\r\n");

    CkJwe jwe;

    // Build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256","zip":"DEF"}
    // The "zip":"DEF" parameter indicates that the plaintext payload should
    // be compressed prior to encryption.
    CkJsonObject jweProtHdr;
    jweProtHdr.AppendString("alg","A128KW");
    jweProtHdr.AppendString("enc","A128CBC-HS256");
    jweProtHdr.AppendString("zip","DEF");
    jwe.SetProtectedHeader(jweProtHdr);

    // Set the AES key wrap key:
    const char *aesWrappingKey = "GawgguFyGrWKav7AX4VKUg";
    jwe.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Encrypt and return the JWE in sbJweCompressed:
    CkStringBuilder sbJweCompressed;
    success = jwe.EncryptSb(sbPlainText,"utf-8",sbJweCompressed);
    if (success != true) {
        strOut.append(jwe.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the compressed JWE:
    strOut.append(sbJweCompressed.getAsString());
    strOut.append("\r\n");
    strOut.append("size of compressed JWE: ");
    strOut.appendInt(sbJweCompressed.get_Length());
    strOut.append("\r\n");

    // Now create a JWE without compression.
    jweProtHdr.Delete("zip");
    // Make sure to update the shared protected header:
    jwe.SetProtectedHeader(jweProtHdr);

    CkStringBuilder sbJweUncompressed;
    success = jwe.EncryptSb(sbPlainText,"utf-8",sbJweUncompressed);
    if (success != true) {
        strOut.append(jwe.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the uncompressed JWE:
    strOut.append(sbJweUncompressed.getAsString());
    strOut.append("\r\n");
    strOut.append("size of uncompressed JWE: ");
    strOut.appendInt(sbJweUncompressed.get_Length());
    strOut.append("\r\n");

    // Decrypting is the same whether compression is used or not.
    // The "zip" header in the JWE indicates that the payload should be 
    // automatically decompressed (inflated) after decrypting.
    CkJwe jwe2;
    success = jwe2.LoadJweSb(sbJweCompressed);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Set the AES wrap key.
    jwe2.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Decrypt (also automatically decompresses).
    CkStringBuilder sbOriginalText;
    success = jwe2.DecryptSb(0,"utf-8",sbOriginalText);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("original text from compressed JWE: ");
    strOut.append("\r\n");
    strOut.append(sbOriginalText.getAsString());
    strOut.append("\r\n");

    // -----------------------------------------------------------
    // Do the same with the uncompressed JWE

    success = jwe2.LoadJweSb(sbJweUncompressed);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Set the AES wrap key.
    jwe2.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Decrypt.
    sbOriginalText.Clear();
    success = jwe2.DecryptSb(0,"utf-8",sbOriginalText);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("original text from uncompressed JWE: ");
    strOut.append("\r\n");
    strOut.append(sbOriginalText.getAsString());
    strOut.append("\r\n");

    // ------------------------------------------------
    // The output of this example is:
    // (Note: Your output data will be different because the content encryption key is randomly generated.)

    // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2IiwiemlwIjoiREVGIn0.xuW-pEAIdEUFnk10m8ocursvktO8Of9ByCCAt6LgKkkOtCWCUn1kQw.zpGj-9WVni3cQxyOuZbcGA.0hzP1myua3oYpUHwCIY_3edBUREbUpLaX6wYuJduOdI.Ppc6aEO3y3B8BJ1FKMPjlA
    // size of compressed JWE: 212
    // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.N4KeyC7nnSFkieJOyE24_zKeuV_m7v5UKoJb1TgV4Yc_r2RzUPNvyA.6AEdyXSCKx-iMmUJyypSLg.QpixfyrwhGpmwUDp623viik4smPav7vwPLiC2r-V-jwnSfEH3mxWu6DbrIz3mixaqATwynmEBzVPxvS9jTXpSAGCnniib4_0WoPl3r_wF5tlsKOEe--jpNso-DKd1Tp8jJxj3JkFWt3IRnUUKGj17g.sBfDwFc5fzpaI-UW8-SW4g
    // size of uncompressed JWE: 303
    // original text from compressed JWE: 
    // Live long and prosper.
    // Live long and prosper.
    // Live long and prosper.
    // Live long and prosper.
    // 
    // original text from uncompressed JWE: 
    // Live long and prosper.
    // Live long and prosper.
    // Live long and prosper.
    // Live long and prosper.
    // 


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }