ChaCha Class

Properties Methods Events Configuration Settings Errors

The ChaCha class can be used to encrypt and decrypt data with the ChaCha20 algorithm.

Syntax

class ipworksencrypt.ChaCha

Remarks

The class implements ChaCha20 as defined in RFC 7539. This may be used to both encrypt and decrypt data. The class also support Authenticated Encryption with Additional Data (AEAD) via AEAD_CHACHA20_POLY1305. To enable the use of AEAD set use_aead to True.

Data may be encrypted and decrypted in its entirety by calling encrypt and decrypt or chunk by chunk by calling encrypt_block and decrypt_block.

In all operations a key and iv must be used. If iv is not set one is automatically generated. key_password may be set in order to automatically generate both a key and iv when a method is called. The same key_password, or key and iv pair are used on both sides of the operation data can be encrypted and decrypted.

Encrypt Notes

encrypt will encrypt the specified data. The following properties are applicable:

iv (required)
key (required)
use_aead (optional)
additional_auth_data (optional - applicable if use_aead is True);

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

output_file
output_message: The output data is written to this property if no other destination is specified.

Additional Notes

The key property must be set to a 256 bit (32 byte) value. This is the only allowed value for ChaCha20. If key_password is set both key and iv will be automatically generated when encrypt is called.

The iv should typically be set to a 96 bit (12 byte) value. See the iv property for details on using a 64 bit (8 byte) value. If iv is not set a 96 bit (12 byte) value will automatically be generated by the class when encrypt is called.

InitialCounter may be set for specific cases where an initial counter of 1 is needed. The default value is 0 and is recommended.

During encryption the on_progress event will fire as data is encrypted.

Encrypt Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[]{ 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };
chacha.InputMessage = "hello chacha!";
chacha.Encrypt();

//chacha.OutputMessageB contains the byte[] of the encrypted data. The above code produces the following encrypted bytes.
// {0x35, 0xBA, 0x31, 0x60, 0x02, 0x77, 0x57, 0x06, 0x5F, 0x6E, 0xE0, 0xD4, 0x76}

AEAD Notes

When encrypting and use_aead is True additional_auth_data optionally holds data that is authenticated but not encrypted.

After encrypting the message the auth_tag property will be populated. To include the auth_tag in the output set IncludeAuthTag to True.

Encrypt with AEAD Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[] { 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };

chacha.UseAEAD = true;
chacha.AdditionalAuthData = "my auth data.";
chacha.InputMessage = "hello chacha!";
chacha.Encrypt();

//chacha.OutputMessageB contains the byte[] of the encrypted data. The above code produces the following encrypted bytes:
// {0x67, 0xF5, 0xC7, 0xE4, 0xE6, 0xD6, 0xC2, 0xF4, 0x09, 0xE3, 0x90, 0xF2, 0x65}

//chacha.AuthTagB contains the byte[] of the AuthTag. The above code produces the following authentication tag:
// {0x46, 0x35, 0xFD, 0x33, 0x30, 0x52, 0xAA, 0x6B, 0xBA, 0x32, 0x16, 0xA6, 0x48, 0x12, 0x52, 0x78}

Encrypt Block Notes

encrypt_block will encrypt the input data and return the encrypted block. The encrypted block will always be the same length as the decrypted data. The following properties are applicable:

iv (required)
key (required)

InputBuffer specifies the input data to encrypt.

LastBlock specifies whether the block is the last block. Required when use_aead is True. When LastBlock is True the class will calculate the auth_tag value. If use_aead is False the value of LastBlock is not used.

EncryptBlock Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[] { 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };
chacha.UseAEAD = true;

byte[] tempEncryptedBlock;

//Encrypt any number of blocks of any size
tempEncryptedBlock = chacha.EncryptBlock(part1, false);
tempEncryptedBlock = chacha.EncryptBlock(part2, false);

//Pass true for the last block
tempEncryptedBlock = chacha.EncryptBlock(part3, true);

//Save AuthTag for use when decrypting
byte[] authTab = chacha.AuthTagB;

Decrypt Notes

decrypt will decrypt the specified data. The following properties are applicable:

iv (required)
key (required)
use_aead (optional)
auth_tag (conditional - required if use_aead is True)
additional_auth_data (optional - applicable if use_aead is True);

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

output_file
output_message: The output data is written to this property if no other destination is specified.

Additional Notes

The key property must be set to the 256 bit (32 byte) value originally used to encrypt the data. iv must be set to the original IV value used to encrypt the data.

If using a password, key_password must be set to the same key_password used when encrypting the data. This will automatically generate both key and iv when decrypt is called.

InitialCounter may be set for specific cases where an initial counter of 1 is needed. The default value is 0 and is recommended.

During decryption the on_progress event will fire as data is decrypted.

Decrypt Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[] { 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };
chacha.InputMessageB = new byte[] { 0x35, 0xBA, 0x31, 0x60, 0x02, 0x77, 0x57, 0x06, 0x5F, 0x6E, 0xE0, 0xD4, 0x76 };
chacha.Decrypt();

Console.WriteLine(chacha.OutputMessage); //outputs "hello chacha!"

AEAD Notes

When decrypting additional_auth_data must be set to the same value that was specified when encrypting. auth_tag must be set to the auth_tag value produced when encrypting.

Note: IncludeAuthTag may be set to True if the auth_tag value was included in the encrypted message.

Decrypt with AEAD Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[] { 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };
chacha.AuthTagB = new byte[] { 0x46, 0x35, 0xFD, 0x33, 0x30, 0x52, 0xAA, 0x6B, 0xBA, 0x32, 0x16, 0xA6, 0x48, 0x12, 0x52, 0x78 };
chacha.InputMessageB = new byte[] { 0x67, 0xF5, 0xC7, 0xE4, 0xE6, 0xD6, 0xC2, 0xF4, 0x09, 0xE3, 0x90, 0xF2, 0x65 };

chacha.UseAEAD = true;
chacha.AdditionalAuthData = "my auth data.";
chacha.Decrypt();

Console.WriteLine(chacha.OutputMessage); //outputs "hello chacha!"

Decrypt Block Notes

decrypt_block will decrypt the input data and return the decrypted block. The decrypted block will always be the same length as the encrypted data. The following properties are applicable:

iv (required)
key (required)

InputBuffer specifies the input data to decrypt.

LastBlock specifies whether the block is the last block. Required when use_aead is True. When LastBlock is True the class will validate the auth_tag value. If use_aead is False the value of LastBlock is not used.

DecryptBlock Example

Chacha chacha = new Chacha();
chacha.KeyB = new byte[] { 0xBB, 0x76, 0x17, 0xC9, 0x05, 0x73, 0x4A, 0x8D, 0x59, 0x9D, 0x7B, 0x0D, 0x86, 0x2A, 0x03, 0x82, 0x50, 0x6A, 0x70, 0xFB, 0xA8, 0x56, 0x47, 0x1B, 0x1E, 0x68, 0x0B, 0x2B, 0x34, 0x18, 0x0F, 0xE2 };
chacha.IVB = new byte[] { 0x0D, 0xE4, 0x43, 0x40, 0x29, 0xAD, 0x70, 0x7D, 0x7B, 0x32, 0xB5, 0xC7 };
chacha.UseAEAD = true;
cahcha.AuthTagB = authTag; //Value calculated during encryption.

byte[] tempDecryptedBlock;

//Decrypt any number of blocks of any size
tempDecryptedBlock = chacha.DecryptBlock(part1, false);
tempDecryptedBlock = chacha.DecryptBlock(part2, false);

//Pass true for the last block
tempDecryptedBlock = chacha.DecryptBlock(part3, true);

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.


additional_auth_data	Additional Authentication Data (AAD) used when UseAEAD is True.
auth_tag	The authentication tag used when UseAEAD is set to True.
input_file	The file to process.
input_message	The message to process.
iv	The initialization vector (IV).
key	The secret key for the symmetric algorithm.
key_password	A password to generate the Key and IV .
output_file	The output file when encrypting or decrypting.
output_message	The output message after processing.
overwrite	Indicates whether or not the class should overwrite files.
use_aead	Whether to use AEAD (Authenticated Encryption with Additional Data).
use_hex	Whether input or output is hex encoded.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.


config	Sets or retrieves a configuration setting.
decrypt	Decrypts the data.
decrypt_block	Decrypts a block and returns the decrypted data.
encrypt	Encrypts the data.
encrypt_block	Encrypts data and returns the encrypted block.
reset	Resets the class.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.


on_error	Information about errors during data delivery.
on_progress	Fired as progress is made.

Configuration Settings

The following is a list of configuration settings for the class with short descriptions. Click on the links for further details.


IncludeAuthTag	Whether to append the authentication tag to the cipher text when UseAEAD is True.
IncludeIV	Whether to prepend the IV to the output data and read the IV from the input data.
InitialCounter	The initial counter value.
IVLength	The IV length in bytes.
KeyPasswordAlgorithm	The hash algorithm used to derive the Key and IV from the KeyPassword property.
KeyPasswordIterations	The number of iterations performed when using KeyPassword to derive the Key and IV.
KeyPasswordSalt	The salt value used in conjunction with the KeyPassword to derive the Key and IV.
BuildInfo	Information about the product's build.
CodePage	The system code page used for Unicode to Multibyte translations.
LicenseInfo	Information about the current license.
ProcessIdleEvents	Whether the class uses its internal event loop to process events when the main thread is idle.
SelectWaitMillis	The length of time in milliseconds the class will wait when DoEvents is called if there are no events to process.
UseInternalSecurityAPI	Tells the class whether or not to use the system security libraries or an internal implementation.

IPWorks Encrypt 2020 Python Edition