C++

Streaming Encryption by Encrypting in Chunks

See more Encryption Examples

Encrypt data in chunks. C++

#include <CkCrypt2.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkCrypt2 crypt;

    crypt.put_CryptAlgorithm("aes");
    crypt.put_CipherMode("cbc");
    crypt.put_KeyLength(128);

    crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F","hex");
    crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F","hex");

    crypt.put_EncodingMode("hex");
    const char *txt1 = "The quick brown fox jumped over the lazy dog.\r\n";
    const char *txt2 = "-\r\n";
    const char *txt3 = "Done.\r\n";

    CkStringBuilder sbEncrypted;

    // Encrypt the 1st chunk:
    // (don't worry about feeding the data to the encryptor in 
    // exact multiples of the encryption algorithm's block size.
    // Chilkat will buffer the data.)
    crypt.put_FirstChunk(true);
    crypt.put_LastChunk(false);
    sbEncrypted.Append(crypt.encryptStringENC(txt1));

    // Encrypt the 2nd chunk
    crypt.put_FirstChunk(false);
    crypt.put_LastChunk(false);
    sbEncrypted.Append(crypt.encryptStringENC(txt2));

    // Now encrypt N more chunks...
    // Remember -- we're doing this in CBC mode, so each call
    // to the encrypt method depends on the state from previous
    // calls...
    crypt.put_FirstChunk(false);
    crypt.put_LastChunk(false);
    int i;
    for (i = 0; i <= 4; i++) {
        sbEncrypted.Append(crypt.encryptStringENC(txt1));
        sbEncrypted.Append(crypt.encryptStringENC(txt2));
    }

    // Now encrypt the last chunk:
    crypt.put_FirstChunk(false);
    crypt.put_LastChunk(true);
    sbEncrypted.Append(crypt.encryptStringENC(txt3));

    std::cout << sbEncrypted.getAsString() << "\r\n";

    // Now decrypt in one call.
    // (The data we're decrypting is both the first AND last chunk.)  
    crypt.put_FirstChunk(true);
    crypt.put_LastChunk(true);
    const char *decryptedText = crypt.decryptStringENC(sbEncrypted.getAsString());

    std::cout << decryptedText << "\r\n";

    // Note: You may decrypt in N chunks by setting the FirstChunk
    // and LastChunk properties prior to calling the Decrypt* methods
    }