decrypt Method
Decrypts the data.
Syntax
def decrypt() -> None: ...
Remarks
on_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 on_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!"