(C#) AES and CHACHA20 Encrypt/Decrypt Text

Demonstrates the use of the new EncryptSb and DecryptSb methods introduced in Chilkat v9.5.0.67 to encrypt/decrypt the contents of StringBuilder objects.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

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

bool success;

// First build a string to be encrypted
Chilkat.StringBuilder sb = new Chilkat.StringBuilder();
int i = 1;
while (i < 10) {
    sb.AppendInt(i);
    sb.Append(" the quick brown fox jumped over the lazy dog.\r\n");
    i = i + 1;
}

Debug.WriteLine(sb.GetAsString());

// The string to be encrypted looks like this:

// 1 the quick brown fox jumped over the lazy dog.
// 2 the quick brown fox jumped over the lazy dog.
// 3 the quick brown fox jumped over the lazy dog.
// 4 the quick brown fox jumped over the lazy dog.
// 5 the quick brown fox jumped over the lazy dog.
// 6 the quick brown fox jumped over the lazy dog.
// ...

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

// Specify the encryption to be used.
// First we'll do AES-128 CBC
crypt.CryptAlgorithm = "aes";
crypt.CipherMode = "cbc";
crypt.KeyLength = 128;

string ivHex = "000102030405060708090A0B0C0D0E0F";
crypt.SetEncodedIV(ivHex,"hex");

string keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F";
crypt.SetEncodedKey(keyHex,"hex");

// When EncryptSb is called, the contents of the source (sb)
// remains unmodified.  The encrypted bytes are written into bdEncrypted.
// If bdEncrypted already contained data, it is replaced with the encrypted bytes.
Chilkat.BinData bdEncrypted = new Chilkat.BinData();
success = crypt.EncryptSb(sb,bdEncrypted);
if (success != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// Examine the encrypted bytes:
Debug.WriteLine(bdEncrypted.GetEncoded("base64_mime"));

// Sample encrypted data:

// 0DdNZ22ckMMJBiaKhAu3wUEfh16XW356NIUsDmNs/xwbHe/p1201OmpfzwXwKktkAefu2pckrBgC
// df+1w8lRo+KAy5n5wlAgMGM/UrsVJsp0BmDPk1vaxKrmrGpSXOVCQs1n2+0atIs5YLiOG+Va3+Mi
// EQNb4YK7bNMmvt0++irBxTiGnkx/RncfKwgkbBUpl2x7yV13MW6lapDT6Md0DKAMsTXFJYGeIdEf
// g2uxDDQzI5gUOUHTMrXQ8paD/K76KKB9Jpp/kAM9z8g/d8KUmuphA7KI64d38xsgOmcITlbhlCQ2
// PDkcU6RRzX0FUTUSMgQukhy0jkLZEjHX9poKJD+iJTOkcQUC3OqR9hKhSrvIgJN4lxdR71MheOoQ
// 2wmvRdq+agTWWh333Vmb6J6yDV79aSpnqEDrA8Ks7Xzciol0gve91+JtVJlJKjWwEzWEU8GxF7Q8
// eaWI70lsC5nTLGcbqgKu6gzkzHlHyHaE2FAQA/d5I2dvfsAYUQCza0Zdyw8mmTtHhlP2Tfxj1uPv
// H4Q7BGuKnx3SWT2CnpbX4091w7KzLAztrbFBo/Tf9w8ZpgTK9k1ryfW9/xnk6rW6iQ==

// Decrypt to restore back to the original:
Chilkat.StringBuilder sbOriginal = new Chilkat.StringBuilder();
success = crypt.DecryptSb(bdEncrypted,sbOriginal);
if (success != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// Examine the original data:
Debug.WriteLine(sbOriginal.GetAsString());

// ----------------------------------------------------------------------------------
// To do chacha20 encryption, just change the settings:

crypt.CryptAlgorithm = "chacha20";
crypt.KeyLength = 256;
// The initial count is the initial block counter for the chacha20 algorithm.
// It can be any integer, but must be set to the same when decrypting.
crypt.InitialCount = 22;

// EncryptSb completely replaces the contents of bdEncrypted.
success = crypt.EncryptSb(sb,bdEncrypted);

// However.. DecryptSb appends the decrypted text to whatever may
// have already existed within sbOriginal.
success = crypt.DecryptSb(bdEncrypted,sbOriginal);

Debug.WriteLine("----");
Debug.WriteLine("The original data should be here twice.  Once from the AES decrypt, and again from the chacha20 decrypt.");
Debug.WriteLine(sbOriginal.GetAsString());
Debug.WriteLine("Success.");