Elgamal Class

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Encrypt and decrypt data with the Elgamal asymmetric key encryption algorithm for public-key cryptography.

Syntax

class ipworksencrypt.Elgamal

Remarks

The ElGamal class is used to encrypt/decrypt data with the Elgamal asymmetric key encryption algorithm for public-key cryptography.

To begin you must either specify an existing key or create a new key. Existing public or private keys may be specified by setting the Key* properties. To create a new key pair call create_key.

After specifying a key, specify the data you wish to encrypt or decrypt. Call the encrypt or decrypt method to perform the operation.

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:

• input_file
• input_message

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.

An Elgamal key is made up of a number of individual parameters.

The public key consists of the following parameters:

• keyp
• keyg
• keyy

The class also includes the key_public_key property which holds the PEM formatted public key for ease of use. This is helpful if you are in control of both signature creation and verification process. When sending the public key to a recipient note that not all implementations will support using the PEM formatted value in key_public_key in which case the individual parameters must be sent.

The private key consists of the following parameters:

• keyp
• keyg
• keyy
• keyx

The class also include the key_private_key property which holds the PEM formatted private key for ease of use. This is helpful for storing the private key more easily.

Property List

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

Method List

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

Event List

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

Config Settings

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

input_file Property

The file to process.

Syntax

def get_input_file() -> str: ...
def set_input_file(value: str) -> None: ...

input_file = property(get_input_file, set_input_file)

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:

• input_file
• input_message

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.

input_message Property

The message to process.

Syntax

def get_input_message() -> bytes: ...
def set_input_message(value: bytes) -> None: ...

input_message = property(get_input_message, set_input_message)

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:

• input_file
• input_message

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.

keyg Property

Represents the G parameter for the Elgamal algorithm.

Syntax

def get_keyg() -> bytes: ...
def set_keyg(value: bytes) -> None: ...

keyg = property(get_keyg, set_keyg)

Default Value

""

Remarks

Represents the G parameter for the Elgamal algorithm.

keyp Property

Represents the P parameter for the Elgamal algorithm.

Syntax

def get_keyp() -> bytes: ...
def set_keyp(value: bytes) -> None: ...

keyp = property(get_keyp, set_keyp)

Default Value

""

Remarks

Represents the P parameter for the Elgamal algorithm.

key_private_key Property

This property is a PEM formatted private key.

Syntax

def get_key_private_key() -> str: ...
def set_key_private_key(value: str) -> None: ...

key_private_key = property(get_key_private_key, set_key_private_key)

Default Value

""

Remarks

This property is a PEM formatted private key. The purpose of this property is to allow easier management of the private key parameters by using only a single value.

key_public_key Property

This property is a PEM formatted public key.

Syntax

def get_key_public_key() -> str: ...
def set_key_public_key(value: str) -> None: ...

key_public_key = property(get_key_public_key, set_key_public_key)

Default Value

""

Remarks

This property is a PEM formatted public key. The purpose of this property is to allow easier management of the public key parameters by using only a single value.

keyx Property

Represents the X parameter for the Elgamal algorithm.

Syntax

def get_keyx() -> bytes: ...
def set_keyx(value: bytes) -> None: ...

keyx = property(get_keyx, set_keyx)

Default Value

""

Remarks

Represents the X parameter for the Elgamal algorithm.

keyy Property

Represents the Y parameter for the Elgamal algorithm.

Syntax

def get_keyy() -> bytes: ...
def set_keyy(value: bytes) -> None: ...

keyy = property(get_keyy, set_keyy)

Default Value

""

Remarks

Represents the Y parameter for the Elgamal algorithm.

output_file Property

The output file when encrypting or decrypting.

Syntax

def get_output_file() -> str: ...
def set_output_file(value: str) -> None: ...

output_file = property(get_output_file, set_output_file)

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:

• input_file
• input_message

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.

output_message Property

The output message after processing.

Syntax

def get_output_message() -> bytes: ...

output_message = property(get_output_message, None)

Default Value

""

Remarks

This property will be populated with the output from the operation if output_file 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:

• input_file
• input_message

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.

This property is read-only.

overwrite Property

Indicates whether or not the class should overwrite files.

Syntax

def get_overwrite() -> bool: ...
def set_overwrite(value: bool) -> None: ...

overwrite = property(get_overwrite, set_overwrite)

Default Value

FALSE

Remarks

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

recipient_keyg Property

Represents the G parameter for the Elgamal algorithm.

Syntax

def get_recipient_keyg() -> bytes: ...
def set_recipient_keyg(value: bytes) -> None: ...

recipient_keyg = property(get_recipient_keyg, set_recipient_keyg)

Default Value

""

Remarks

Represents the G parameter for the Elgamal algorithm.

recipient_keyp Property

Represents the P parameter for the Elgamal algorithm.

Syntax

def get_recipient_keyp() -> bytes: ...
def set_recipient_keyp(value: bytes) -> None: ...

recipient_keyp = property(get_recipient_keyp, set_recipient_keyp)

Default Value

""

Remarks

Represents the P parameter for the Elgamal algorithm.

recipient_key_public_key Property

This property is a PEM formatted public key.

Syntax

def get_recipient_key_public_key() -> str: ...
def set_recipient_key_public_key(value: str) -> None: ...

recipient_key_public_key = property(get_recipient_key_public_key, set_recipient_key_public_key)

Default Value

""

Remarks

This property is a PEM formatted public key. The purpose of this property is to allow easier management of the public key parameters by using only a single value.

recipient_keyy Property

Represents the Y parameter for the Elgamal algorithm.

Syntax

def get_recipient_keyy() -> bytes: ...
def set_recipient_keyy(value: bytes) -> None: ...

recipient_keyy = property(get_recipient_keyy, set_recipient_keyy)

Default Value

""

Remarks

Represents the Y parameter for the Elgamal algorithm.

use_hex Property

Whether input or output is hex encoded.

Syntax

def get_use_hex() -> bool: ...
def set_use_hex(value: bool) -> None: ...

use_hex = property(get_use_hex, set_use_hex)

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. output_message or output_file will hold hex encoded data.

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

config Method

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

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.

create_key Method

Creates a new key.

Syntax

def create_key() -> None: ...

Remarks

This method creates a new public and private key.

When calling create_key the Key* properties are populated with a new private and public key.

An Elgamal key is made up of a number of individual parameters.

The public key consists of the following parameters:

• keyp
• keyg
• keyy

The class also includes the key_public_key property which holds the PEM formatted public key for ease of use. This is helpful if you are in control of both signature creation and verification process. When sending the public key to a recipient note that not all implementations will support using the PEM formatted value in key_public_key in which case the individual parameters must be sent.

The private key consists of the following parameters:

• keyp
• keyg
• keyy
• keyx

The class also include the key_private_key property which holds the PEM formatted private key for ease of use. This is helpful for storing the private key more easily.

decrypt Method

Decrypts the input data using the specified private key.

Syntax

def decrypt() -> None: ...

Remarks

This method decrypts the input data using the private key specified in the Key* properties. Alternatively, a certificate may be specified by setting certificate

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:

• input_file
• input_message

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.

Key Size and the Maximum Length of Data

RSA has an upper limit to the amount of data that can be encrypted or decrypted, also known as message length. This can typically be calculated as the size of the key minus the size of the RSA header and padding.

When not using OAEP, the following formula and table can be referenced. (RSA Key Bytes) - (Header Bytes) = Length of data, where Header Bytes is always 11.

When using OAEP, the following formula and table can be referenced. (RSA Key Bytes) - (2 * Hash Length Bytes) - 2 = Length of data. The table below assumes SHA-256 for the hash, so Hash Length Bytes is 32.

encrypt Method

Encrypts the input data using the recipient's public key.

Syntax

def encrypt() -> None: ...

Remarks

This method encrypts the input data using the public key specified in the RecipientKey* properties. Alternatively, a certificate may be specified by setting recipient_cert

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:

• input_file
• input_message

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.

Key Size and the Maximum Length of Data

RSA has an upper limit to the amount of data that can be encrypted or decrypted, also known as message length. This can typically be calculated as the size of the key minus the size of the RSA header and padding.

When not using OAEP, the following formula and table can be referenced. (RSA Key Bytes) - (Header Bytes) = Length of data, where Header Bytes is always 11.

When using OAEP, the following formula and table can be referenced. (RSA Key Bytes) - (2 * Hash Length Bytes) - 2 = Length of data. The table below assumes SHA-256 for the hash, so Hash Length Bytes is 32.

reset Method

Resets the class.

Syntax

def reset() -> None: ...

Remarks

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

on_error Event

Information about errors during data delivery.

Syntax

class ElgamalErrorEventParams(object):
  @property
  def error_code() -> int: ...

  @property
  def description() -> str: ...

# In class Elgamal:
@property
def on_error() -> Callable[[ElgamalErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[ElgamalErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

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

Elgamal Config Settings

The class accepts one or more of the following configuration settings. Configuration 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.

Elgamal Config Settings

Base Config Settings

Elgamal Errors

Elgamal Errors

	102   No Key specified.
	104   Cannot read or write file.
	105   key parameters incorrect.
	111   OutputFile already exists and Overwrite is False.
	112   Invalid length of input message.
	304   Cannot write file.
	305   Cannot read file.
	306   Cannot create file.
	1301   Specified ElGamal parameters are invalid.
	1302   Missing the data to encrypt/decrypt.
	1303   Public key must be specified.
	1304   Key must be specified.
	1305   Invalid cipher length. The data may not have been encrypted with the public key corresponding to the specified private key data.
	1306   Invalid cipher text. The data may not have been encrypted with the public key corresponding to the specified private key data.
	1307   Inadequate padding. The data may not have been encrypted with the public key corresponding to the specified private key data.
	1308   Missing delimiter. The data may not have been encrypted with the public key corresponding to the specified private key data.
	1309   Message too long.