Elgamal Module

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

Syntax

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 CreateKey.

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:

• 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.

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 KeyPublicKey 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 KeyPublicKey in which case the individual parameters must be sent.

The private key consists of the following parameters:

• KeyP
• KeyG
• KeyY
• KeyX

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.

InputFile Property (Elgamal 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 (Elgamal 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.

Key Property (Elgamal Module)

The Elgamal key used for decryption.

Syntax

• Swift
• Objective-C

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

@property (nonatomic,readwrite,assign,getter=keyG,setter=setKeyG:) NSString* keyG;

- (NSString*)keyG;
- (void)setKeyG :(NSString*)newKeyG;

@property (nonatomic,readwrite,assign,getter=keyGB,setter=setKeyGB:) NSData* keyGB;

- (NSData*)keyGB;
- (void)setKeyGB :(NSData*)newKeyG;
@property (nonatomic,readwrite,assign,getter=keyP,setter=setKeyP:) NSString* keyP;

- (NSString*)keyP;
- (void)setKeyP :(NSString*)newKeyP;

@property (nonatomic,readwrite,assign,getter=keyPB,setter=setKeyPB:) NSData* keyPB;

- (NSData*)keyPB;
- (void)setKeyPB :(NSData*)newKeyP;
@property (nonatomic,readwrite,assign,getter=keyPrivateKey,setter=setKeyPrivateKey:) NSString* keyPrivateKey;

- (NSString*)keyPrivateKey;
- (void)setKeyPrivateKey :(NSString*)newKeyPrivateKey;

@property (nonatomic,readwrite,assign,getter=keyPublicKey,setter=setKeyPublicKey:) NSString* keyPublicKey;

- (NSString*)keyPublicKey;
- (void)setKeyPublicKey :(NSString*)newKeyPublicKey;

@property (nonatomic,readwrite,assign,getter=keyX,setter=setKeyX:) NSString* keyX;

- (NSString*)keyX;
- (void)setKeyX :(NSString*)newKeyX;

@property (nonatomic,readwrite,assign,getter=keyXB,setter=setKeyXB:) NSData* keyXB;

- (NSData*)keyXB;
- (void)setKeyXB :(NSData*)newKeyX;
@property (nonatomic,readwrite,assign,getter=keyY,setter=setKeyY:) NSString* keyY;

- (NSString*)keyY;
- (void)setKeyY :(NSString*)newKeyY;

@property (nonatomic,readwrite,assign,getter=keyYB,setter=setKeyYB:) NSData* keyYB;

- (NSData*)keyYB;
- (void)setKeyYB :(NSData*)newKeyY;
 

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.

OutputFile Property (Elgamal 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 (Elgamal 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 (Elgamal 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.

RecipientKey Property (Elgamal Module)

The recipient's public key used when encrypting.

Syntax

• Swift
• Objective-C

public var recipientKey: ElgamalKey {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=recipientKeyG,setter=setRecipientKeyG:) NSString* recipientKeyG;

- (NSString*)recipientKeyG;
- (void)setRecipientKeyG :(NSString*)newRecipientKeyG;

@property (nonatomic,readwrite,assign,getter=recipientKeyGB,setter=setRecipientKeyGB:) NSData* recipientKeyGB;

- (NSData*)recipientKeyGB;
- (void)setRecipientKeyGB :(NSData*)newRecipientKeyG;
@property (nonatomic,readwrite,assign,getter=recipientKeyP,setter=setRecipientKeyP:) NSString* recipientKeyP;

- (NSString*)recipientKeyP;
- (void)setRecipientKeyP :(NSString*)newRecipientKeyP;

@property (nonatomic,readwrite,assign,getter=recipientKeyPB,setter=setRecipientKeyPB:) NSData* recipientKeyPB;

- (NSData*)recipientKeyPB;
- (void)setRecipientKeyPB :(NSData*)newRecipientKeyP;
@property (nonatomic,readwrite,assign,getter=recipientKeyPublicKey,setter=setRecipientKeyPublicKey:) NSString* recipientKeyPublicKey;

- (NSString*)recipientKeyPublicKey;
- (void)setRecipientKeyPublicKey :(NSString*)newRecipientKeyPublicKey;

@property (nonatomic,readwrite,assign,getter=recipientKeyY,setter=setRecipientKeyY:) NSString* recipientKeyY;

- (NSString*)recipientKeyY;
- (void)setRecipientKeyY :(NSString*)newRecipientKeyY;

@property (nonatomic,readwrite,assign,getter=recipientKeyYB,setter=setRecipientKeyYB:) NSData* recipientKeyYB;

- (NSData*)recipientKeyYB;
- (void)setRecipientKeyYB :(NSData*)newRecipientKeyY;
 

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.

UseHex Property (Elgamal 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.

Config Method (Elgamal 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.

CreateKey Method (Elgamal Module)

Creates a new key.

Syntax

• Swift
• Objective-C

public func createKey() throws -> Void

- (void)createKey;

Remarks

This method creates a new public and private key.

When calling CreateKey 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 KeyPublicKey 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 KeyPublicKey in which case the individual parameters must be sent.

The private key consists of the following parameters:

• KeyP
• KeyG
• KeyY
• KeyX

Decrypt Method (Elgamal Module)

Decrypts the input data using the specified private key.

Syntax

• Swift
• Objective-C

public func decrypt() throws -> Void

- (void)decrypt;

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:

• 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.

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 (Elgamal Module)

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

Syntax

• Swift
• Objective-C

public func encrypt() throws -> Void

- (void)encrypt;

Remarks

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

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.

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 (Elgamal 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 (Elgamal Module)

Information 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 .

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.

ElgamalKey Type

Contains the typical parameters for the Elgamal algorithm.

Remarks

This type is made up of fields that represent the private and public key parameters used by the Elgamal algorithm.

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 KeyPublicKey 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 KeyPublicKey in which case the individual parameters must be sent.

The private key consists of the following parameters:

• KeyP
• KeyG
• KeyY
• KeyX

Fields

Constructors

public init()

The default constructor creates a new ElgamalKey instance but does not assign a public or private key.

public init(p: , g: , y: )

The public key constructor assigns an existing public key.

public init(p: , g: , y: , x: )

The private key constructor assigns an existing private key.

Config Settings (Elgamal Module)

Trappable Errors (Elgamal Module)

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.