ChaCha Module

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

Syntax

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 UseAEAD to True.

Data may be encrypted and decrypted in its entirety by calling Encrypt and Decrypt or chunk by chunk by calling EncryptBlock and DecryptBlock.

In all operations a Key and IV must be used. If IV is not set one is automatically generated. KeyPassword may be set in order to automatically generate both a Key and IV when a method is called. The same KeyPassword, 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)
• UseAEAD (optional)
• AdditionalAuthData (optional - applicable if UseAEAD 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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: 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 KeyPassword 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 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 UseAEAD is True AdditionalAuthData optionally holds data that is authenticated but not encrypted.

After encrypting the message the AuthTag property will be populated. To include the AuthTag 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

EncryptBlock 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 UseAEAD is True. When LastBlock is True the class will calculate the AuthTag value. If UseAEAD 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)
• UseAEAD (optional)
• AuthTag (conditional - required if UseAEAD is True)
• AdditionalAuthData (optional - applicable if UseAEAD 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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: 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, KeyPassword must be set to the same KeyPassword 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 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 AdditionalAuthData must be set to the same value that was specified when encrypting. AuthTag must be set to the AuthTag value produced when encrypting.

Note: IncludeAuthTag may be set to True if the AuthTag 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

DecryptBlock 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 UseAEAD is True. When LastBlock is True the class will validate the AuthTag value. If UseAEAD 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 module with short descriptions. Click on the links for further details.

Method List

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

Event List

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

Config Settings

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

AdditionalAuthData Property (ChaCha Module)

Additional Authentication Data (AAD) used when UseAEAD is True.

Syntax

• Swift
• Objective-C

public var additionalAuthData: String {
  get {...}
  set {...}
}

public var additionalAuthDataB: Data {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=additionalAuthData,setter=setAdditionalAuthData:) NSString* additionalAuthData;

- (NSString*)additionalAuthData;
- (void)setAdditionalAuthData :(NSString*)newAdditionalAuthData;

@property (nonatomic,readwrite,assign,getter=additionalAuthDataB,setter=setAdditionalAuthDataB:) NSData* additionalAuthDataB;

- (NSData*)additionalAuthDataB;
- (void)setAdditionalAuthDataB :(NSData*)newAdditionalAuthData;

Default Value

""

Remarks

This property specifies data that is authentication but not encrypted. This is only applicable when UseAEAD is True.

Note that AAD data is authenticated but not encrypted, so it is not included in the output.

AuthTag Property (ChaCha Module)

The authentication tag used when UseAEAD is set to True.

Syntax

• Swift
• Objective-C

public var authTag: String {
  get {...}
  set {...}
}

public var authTagB: Data {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=authTag,setter=setAuthTag:) NSString* authTag;

- (NSString*)authTag;
- (void)setAuthTag :(NSString*)newAuthTag;

@property (nonatomic,readwrite,assign,getter=authTagB,setter=setAuthTagB:) NSData* authTagB;

- (NSData*)authTagB;
- (void)setAuthTagB :(NSData*)newAuthTag;

Default Value

""

Remarks

This property holds the 128 bit authentication tag used when UseAEAD is set to True. It is only applicable when UseAEAD is True.

This is populated after calling Encrypt. To also include the value in the output set IncludeAuthTag to True.

This must be set before calling Decrypt. If the auth tag is included in the encrypted data set IncludeAuthTag to True before calling Decrypt.

InputFile Property (ChaCha Module)

The file to process.

Syntax

• Swift
• Objective-C

public var inputFile: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=inputFile,setter=setInputFile:) NSString* inputFile;

- (NSString*)inputFile;
- (void)setInputFile :(NSString*)newInputFile;

Default Value

""

Remarks

This property specifies the file to be processed. Set this property to the full or relative path to the file which will be processed.

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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

InputMessage Property (ChaCha Module)

The message to process.

Syntax

• Swift
• Objective-C

public var inputMessage: String {
  get {...}
  set {...}
}

public var inputMessageB: Data {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=inputMessage,setter=setInputMessage:) NSString* inputMessage;

- (NSString*)inputMessage;
- (void)setInputMessage :(NSString*)newInputMessage;

@property (nonatomic,readwrite,assign,getter=inputMessageB,setter=setInputMessageB:) NSData* inputMessageB;

- (NSData*)inputMessageB;
- (void)setInputMessageB :(NSData*)newInputMessage;

Default Value

""

Remarks

This property specifies the message to be processed.

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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

IV Property (ChaCha Module)

The initialization vector (IV).

Syntax

• Swift
• Objective-C

public var iv: String {
  get {...}
  set {...}
}

public var ivB: Data {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=IV,setter=setIV:) NSString* IV;

- (NSString*)IV;
- (void)setIV :(NSString*)newIV;

@property (nonatomic,readwrite,assign,getter=IVB,setter=setIVB:) NSData* IVB;

- (NSData*)IVB;
- (void)setIVB :(NSData*)newIV;

Default Value

""

Remarks

This property specifies the initialization vector (IV). This is also referred to as the nonce. By default this property is empty and the class will automatically generate a new IV value if KeyPassword or Key is set before Encrypt or EncryptBlock is called.

The size of the IV may be either 96 bits in length (12 bytes) or 64 bits in length (8 bytes).

Compatibility Notes

A 96 bit length value is used for implementations implementing RFC 7539. A 64 bit length value may be used by implementations that follow the original draft of ChaCha. When using a 96 bit length value the maximum file size of data is 256 GB.

If another entity is performing the decryption and it is not known whether it supports 64 bit length values, choose a 96 bit length value by default. This follows the RFC and should be the most widely implemented value.

The class supports both lengths.

Note: If Key is specified but IV is not, an IV will be automatically generated. To control the length of the IV that is generated set IVLength.

Key Property (ChaCha Module)

The secret key for the symmetric algorithm.

Syntax

• Swift
• Objective-C

public var key: String {
  get {...}
  set {...}
}

public var keyB: Data {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=key,setter=setKey:) NSString* key;

- (NSString*)key;
- (void)setKey :(NSString*)newKey;

@property (nonatomic,readwrite,assign,getter=keyB,setter=setKeyB:) NSData* keyB;

- (NSData*)keyB;
- (void)setKeyB :(NSData*)newKey;

Default Value

""

Remarks

This secret key is used both for encryption and decryption. The secret key should be known only to the sender and the receiver. This key must be 256 bits in length (32 bytes).

If this property is left empty and KeyPassword is specified, a Key value will be generated by the class as necessary.

KeyPassword Property (ChaCha Module)

A password to generate the Key and IV .

Syntax

• Swift
• Objective-C

public var keyPassword: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=keyPassword,setter=setKeyPassword:) NSString* keyPassword;

- (NSString*)keyPassword;
- (void)setKeyPassword :(NSString*)newKeyPassword;

Default Value

""

Remarks

When this property is set the class will calculate values for Key and IV using the PKCS5 password digest algorithm. This provides a simpler alternative to creating and managing Key and IV values directly.

OutputFile Property (ChaCha Module)

The output file when encrypting or decrypting.

Syntax

• Swift
• Objective-C

public var outputFile: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=outputFile,setter=setOutputFile:) NSString* outputFile;

- (NSString*)outputFile;
- (void)setOutputFile :(NSString*)newOutputFile;

Default Value

""

Remarks

This property specifies the file to which the output will be written when Encrypt or Decrypt is called. This may be set to an absolute or relative path.

This property is only applicable to Encrypt and Decrypt.

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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

OutputMessage Property (ChaCha Module)

The output message after processing.

Syntax

• Swift
• Objective-C

public var outputMessage: String {
  get {...}
}

public var outputMessageB: Data {
  get {...}
}

@property (nonatomic,readonly,assign,getter=outputMessage) NSString* outputMessage;

- (NSString*)outputMessage;

@property (nonatomic,readonly,assign,getter=outputMessageB) NSData* outputMessageB;

- (NSData*)outputMessageB;

Default Value

""

Remarks

This property will be populated with the output from the operation if OutputFile is not set.

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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

This property is read-only.

Overwrite Property (ChaCha Module)

Indicates whether or not the module should overwrite files.

Syntax

• Swift
• Objective-C

public var overwrite: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=overwrite,setter=setOverwrite:) BOOL overwrite;

- (BOOL)overwrite;
- (void)setOverwrite :(BOOL)newOverwrite;

Default Value

False

Remarks

This property indicates whether or not the class will overwrite OutputFile. If Overwrite is False, an error will be thrown whenever OutputFile exists before an operation. The default value is False.

UseAEAD Property (ChaCha Module)

Whether to use AEAD (Authenticated Encryption with Additional Data).

Syntax

• Swift
• Objective-C

public var useAEAD: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=useAEAD,setter=setUseAEAD:) BOOL useAEAD;

- (BOOL)useAEAD;
- (void)setUseAEAD :(BOOL)newUseAEAD;

Default Value

False

Remarks

If this property is set to True the class uses the algorithm AEAD_CHACHA20_POLY1305 as defined in RFC 7539 to construct a message using AEAD. See Encrypt and Decrypt for details.

UseHex Property (ChaCha Module)

Whether input or output is hex encoded.

Syntax

• Swift
• Objective-C

public var useHex: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=useHex,setter=setUseHex:) BOOL useHex;

- (BOOL)useHex;
- (void)setUseHex :(BOOL)newUseHex;

Default Value

False

Remarks

This property specifies whether the encrypted data is hex encoded.

If set to True, when Encrypt is called the class will perform the encryption as normal and then hex encode the output. OutputMessage or OutputFile will hold hex encoded data.

If set to True, when Decrypt is called the class will expect InputMessage or InputFile to hold hex encoded data. The class will then hex decode the data and perform decryption as normal.

AEAD Notes

When UseAEAD is set to True this property also applies to AuthTag. After calling Encrypt AuthTag will hold a hex encoded value. Before calling Decrypt AuthTag must be set to a hex encoded value.

Config Method (ChaCha Module)

Sets or retrieves a configuration setting.

Syntax

• Swift
• Objective-C

public func config(configurationString: String) throws -> String

- (NSString*)config:(NSString*)configurationString;

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Decrypt Method (ChaCha Module)

Decrypts the data.

Syntax

• Swift
• Objective-C

public func decrypt() throws -> Void

- (void)decrypt;

Remarks

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

• IV (required)
• Key (required)
• UseAEAD (optional)
• AuthTag (conditional - required if UseAEAD is True)
• AdditionalAuthData (optional - applicable if UseAEAD 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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: 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, KeyPassword must be set to the same KeyPassword 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 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 AdditionalAuthData must be set to the same value that was specified when encrypting. AuthTag must be set to the AuthTag value produced when encrypting.

Note: IncludeAuthTag may be set to True if the AuthTag 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!"

DecryptBlock Method (ChaCha Module)

Decrypts a block and returns the decrypted data.

Syntax

• Swift
• Objective-C

public func decryptBlock(inputBuffer: Data, lastBlock: Bool) throws -> Data

- (NSData*)decryptBlock:(NSData*)inputBuffer :(BOOL)lastBlock;

Remarks

DecryptBlock 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 UseAEAD is True. When LastBlock is True the class will validate the AuthTag value. If UseAEAD 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);

Encrypt Method (ChaCha Module)

Encrypts the data.

Syntax

• Swift
• Objective-C

public func encrypt() throws -> Void

- (void)encrypt;

Remarks

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

• IV (required)
• Key (required)
• UseAEAD (optional)
• AdditionalAuthData (optional - applicable if UseAEAD 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:

• InputFile
• InputMessage

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

• OutputFile
• OutputMessage: 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 KeyPassword 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 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 UseAEAD is True AdditionalAuthData optionally holds data that is authenticated but not encrypted.

After encrypting the message the AuthTag property will be populated. To include the AuthTag 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}

EncryptBlock Method (ChaCha Module)

Encrypts data and returns the encrypted block.

Syntax

• Swift
• Objective-C

public func encryptBlock(inputBuffer: Data, lastBlock: Bool) throws -> Data

- (NSData*)encryptBlock:(NSData*)inputBuffer :(BOOL)lastBlock;

Remarks

EncryptBlock 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 UseAEAD is True. When LastBlock is True the class will calculate the AuthTag value. If UseAEAD 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;

Reset Method (ChaCha Module)

Resets the component.

Syntax

• Swift
• Objective-C

public func reset() throws -> Void

- (void)reset;

Remarks

When called, the class will reset all of its properties to their default values.

Error Event (ChaCha Module)

Fired when information is available about errors during data delivery.

Syntax

• Swift
• Objective-C

func onError(errorCode: Int32, description: String)

- (void)onError:(int)errorCode :(NSString*)description;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class .

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Progress Event (ChaCha Module)

Fired as progress is made.

Syntax

• Swift
• Objective-C

func onProgress(bytesProcessed: Int64, percentProcessed: Int32)

- (void)onProgress:(long long)bytesProcessed :(int)percentProcessed;

Remarks

This event is fired automatically as data is processed by the class.

The PercentProcessed parameter indicates the current status of the operation.

The BytesProcessed parameter holds the total number of bytes processed so far.

Config Settings (ChaCha Module)

ChaCha Config Settings

Base Config Settings

Trappable Errors (ChaCha Module)

ChaCha Errors