(C) ChaCha20 Encryption

Demonstrates ChaCha20 encryption and decryption. (Introduced in Chilkat v9.5.0.55) This example duplicates the results of Test Vector #3 for ChaCha20 Encryption in RFC 7539.

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#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    const char *ivHex;
    const char *keyHex;
    const char *plainText;
    const char *encStr;
    const char *decStr;

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

    crypt = CkCrypt2_Create();

    // Set the encryption algorithm to chacha20
    // chacha20 is a stream cipher, and therefore no cipher mode applies.
    CkCrypt2_putCryptAlgorithm(crypt,"chacha20");

    // The key length for chacha20 is always 256-bits.
    CkCrypt2_putKeyLength(crypt,256);

    // Note: "padding" only applies to block encryption algorithmns.
    // Since chacha20 is a stream cipher, there is no padding and the output
    // number of bytes is exactly equal to the input.

    // EncodingMode specifies the encoding of the output for
    // encryption, and the input for decryption.
    // Valid modes are (case insensitive) "Base64", "modBase64", "Base32", "Base58", "UU", 
    // "QP" (for quoted-printable), "URL" (for url-encoding), "Hex", 
    // "Q", "B", "url_oauth", "url_rfc1738", "url_rfc2396", and "url_rfc3986".
    CkCrypt2_putEncodingMode(crypt,"hex");

    // The inputs to ChaCha20 encryption, specified by RFC 7539, are:
    // 1) A 256-bit secret key.
    // 2) A 96-bit nonce.
    // 3) A 32-bit initial count.
    // The IV property is used to specify the chacha20 nonce.
    // For a 96-bit nonce, the IV should be 12 bytes in length.
    // 
    // Note: Some implementations of chacha20, such as that used internally by SSH,
    // use a 64-bit nonce and 64-bit count.  To do chacha20 encryption in this way,
    // simply provide 8 bytes for the IV instead of 12 bytes.  Chilkat will then automatically
    // use 8 bytes (64-bits) for the count. 

    // This example duplicates Test Vector #3 (for ChaCha20 encryption) from RFC 7539.
    ivHex = "000000000000000000000002";
    CkCrypt2_SetEncodedIV(crypt,ivHex,"hex");

    CkCrypt2_putInitialCount(crypt,42);

    keyHex = "1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0";
    CkCrypt2_SetEncodedKey(crypt,keyHex,"hex");

    plainText = "'Twas brillig, and the slithy toves\nDid gyre and gimble in the wabe:\nAll mimsy were the borogoves,\nAnd the mome raths outgrabe.";

    encStr = CkCrypt2_encryptStringENC(crypt,plainText);
    printf("%s\n",encStr);

    // Now decrypt:
    decStr = CkCrypt2_decryptStringENC(crypt,encStr);
    printf("%s\n",decStr);

    // Here is the Test Vector data copied from RFC 7539

    //  Test Vector #3:
    //  ==============
    // 
    //  Key:
    //  000  1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0  ..@..U...3......
    //  016  47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0  G9..@+....\. pu.
    // 
    //  Nonce:
    //  000  00 00 00 00 00 00 00 00 00 00 00 02              ............
    // 
    //  Initial Block Counter = 42
    // 
    //  Plaintext:
    //  000  27 54 77 61 73 20 62 72 69 6c 6c 69 67 2c 20 61  'Twas brillig, a
    //  016  6e 64 20 74 68 65 20 73 6c 69 74 68 79 20 74 6f  nd the slithy to
    //  032  76 65 73 0a 44 69 64 20 67 79 72 65 20 61 6e 64  ves.Did gyre and
    //  048  20 67 69 6d 62 6c 65 20 69 6e 20 74 68 65 20 77   gimble in the w
    //  064  61 62 65 3a 0a 41 6c 6c 20 6d 69 6d 73 79 20 77  abe:.All mimsy w
    //  080  65 72 65 20 74 68 65 20 62 6f 72 6f 67 6f 76 65  ere the borogove
    //  096  73 2c 0a 41 6e 64 20 74 68 65 20 6d 6f 6d 65 20  s,.And the mome
    //  112  72 61 74 68 73 20 6f 75 74 67 72 61 62 65 2e     raths outgrabe.
    // 
    //  Ciphertext:
    //  000  62 e6 34 7f 95 ed 87 a4 5f fa e7 42 6f 27 a1 df  b.4....._..Bo'..
    //  016  5f b6 91 10 04 4c 0d 73 11 8e ff a9 5b 01 e5 cf  _....L.s....[...
    //  032  16 6d 3d f2 d7 21 ca f9 b2 1e 5f b1 4c 61 68 71  .m=..!...._.Lahq
    //  048  fd 84 c5 4f 9d 65 b2 83 19 6c 7f e4 f6 05 53 eb  ...O.e...l....S.
    //  064  f3 9c 64 02 c4 22 34 e3 2a 35 6b 3e 76 43 12 a6  ..d.."4.*5k>vC..
    //  080  1a 55 32 05 57 16 ea d6 96 25 68 f8 7d 3f 3f 77  .U2.W....%h.}??w
    //  096  04 c6 a8 d1 bc d1 bf 4d 50 d6 15 4b 6d a7 31 b1  .......MP..Km.1.
    //  112  87 b5 8d fd 72 8a fa 36 75 7a 79 7a c1 88 d1     ....r..6uzyz..


    CkCrypt2_Dispose(crypt);

    }