HMAC Class

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The HMAC class may be used to produce a MAC (or Tag) value using the HMAC algorithm.

Syntax

ipworksencrypt.HMAC

Remarks

The HMAC component allows you to compute a MAC value using various algorithms including HMACMD5, HMACSHA1, HMACSHA224, HMACSHA256, HMACSHA384, HMACSHA512, etc.

ComputeMAC Notes

ComputeMAC computes the MAC (Message Authentication Code) from the input data.

Before calling this method set Key to a key. If EncodeMAC is set to True (default) the output data will be hex encoded.

Input Notes

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

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

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops.

After calling this method MACValue will be populated with the computed MAC value.

ComputeMAC Example

HMAC hmac = new HMAC(); hmac.Algorithm = HMACAlgorithms.hmacSHA256; hmac.KeyB = new byte[] { 0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a, 0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0, 0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09, 0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0 }; hmac.InputMessage = "Hello HMAC"; hmac.EncodeMAC = true; //hex output hmac.ComputeMAC(); //This outputs "FDFB2DD7121E743D933718E165659A46DF431CFBCCDEA121C68CE13EA83153B3" Console.WriteLine(hmac.MACValue);

ComputeMACBlock Notes

ComputeMACBlock allows input to the class to be specified in blocks. This method will return the MAC value only when the parameter LastBlock is True.

InputBuffer specifies the input data.

LastBlock specifies whether the block is the last block. If this is False the method will return an empty byte array.

To calculate the MAC value of data that is broken apart into multiple blocks make multiple calls to this method. For instance: //Encode output in hex hmac.EncodeMAC = true; //hex output //Pass any number of parts, of any size hmac.ComputeMACBlock(part1,false); hmac.ComputeMACBlock(part2,false); hmac.ComputeMACBlock(part3,false); //Pass true for the last block hmac.ComputeMACBlock(lastPart,true); //The MACValue property holds the MAC value Console.WriteLine(hmac.MACValue);

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.

Algorithm Property (HMAC Class)

The algorithm used to create the HMAC.

Syntax

public int getAlgorithm();
public void setAlgorithm(int algorithm);

Enumerated values:
  public final static int hmacMD5 = 0;
  public final static int hmacSHA1 = 1;
  public final static int hmacSHA224 = 2;
  public final static int hmacSHA256 = 3;
  public final static int hmacSHA384 = 4;
  public final static int hmacSHA512 = 5;
  public final static int hmacRIPEMD160 = 6;

Default Value

3

Remarks

This property specifies the algorithm used when calling ComputeMAC. Possible values are:

EncodeMAC Property (HMAC Class)

Whether the MAC value is hex encoded.

Syntax

public boolean isEncodeMAC();
public void setEncodeMAC(boolean encodeMAC);

Default Value

True

Remarks

This property specifies whether the computed MAC value is hex encoded. When set to True (default) the class will hex encode the computed MAC for easier use. Set this value to False to obtain the MAC value in an unmodified form.

The default value is True.

InputFile Property (HMAC Class)

The file to process.

Syntax

public String getInputFile();
public void setInputFile(String inputFile);

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:

• SetInputStream
• InputFile
• InputMessage

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

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

When using streams, you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

InputMessage Property (HMAC Class)

The message to process.

Syntax

public byte[] getInputMessage();
public void setInputMessage(byte[] inputMessage);

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:

• SetInputStream
• InputFile
• InputMessage

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

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

When using streams, you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Key Property (HMAC Class)

The key to be used when computing a MAC (Message Authentication Code).

Syntax

public byte[] getKey();
public void setKey(byte[] key);

Default Value

""

Remarks

This property holds the secret key used when computing the MACValue. The key can be arbitrarily long.

It is recommended that the length of the key be equal to or larger than the hash size of the algorithm. Use of keys shorter than the hash size is discouraged.

Sizes (in bytes)

Key Length Details

As mentioned above it is recommended to use a key size equal to the hash size. Use of keys larger than the hash size does not typically significantly increase the function strength. Keys of any length are technically valid however see the below processing rules to understand how keys of varying lengths are treated:

• If the key length is equal to the hash size (recommended) it is used without modification.
• If the key length is less than the hash size it is used without modification.
• If the key length is less than or equal to the block size it is used without modification.
• If the key length is larger than the block size it is first hashed with the same algorithm.

MACValue Property (HMAC Class)

The computed MAC value.

Syntax

public byte[] getMACValue();

Default Value

""

Remarks

The computed MAC value. This property is populated after calling ComputeMAC.

This property is read-only.

ComputeMAC Method (HMAC Class)

Computes the MAC.

Syntax

public void computeMAC();

Remarks

ComputeMAC computes the MAC (Message Authentication Code) from the input data.

Before calling this method set Key to a key. If EncodeMAC is set to True (default) the output data will be hex encoded.

Input Notes

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

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

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops.

After calling this method MACValue will be populated with the computed MAC value.

ComputeMAC Example

HMAC hmac = new HMAC(); hmac.Algorithm = HMACAlgorithms.hmacSHA256; hmac.KeyB = new byte[] { 0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a, 0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0, 0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09, 0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0 }; hmac.InputMessage = "Hello HMAC"; hmac.EncodeMAC = true; //hex output hmac.ComputeMAC(); //This outputs "FDFB2DD7121E743D933718E165659A46DF431CFBCCDEA121C68CE13EA83153B3" Console.WriteLine(hmac.MACValue);

ComputeMACBlock Method (HMAC Class)

Computes the MAC value of specified data.

Syntax

public byte[] computeMACBlock(byte[] inputBuffer, boolean lastBlock);

Remarks

ComputeMACBlock allows input to the class to be specified in blocks. This method will return the MAC value only when the parameter LastBlock is True.

InputBuffer specifies the input data.

LastBlock specifies whether the block is the last block. If this is False the method will return an empty byte array.

To calculate the MAC value of data that is broken apart into multiple blocks make multiple calls to this method. For instance: //Encode output in hex hmac.EncodeMAC = true; //hex output //Pass any number of parts, of any size hmac.ComputeMACBlock(part1,false); hmac.ComputeMACBlock(part2,false); hmac.ComputeMACBlock(part3,false); //Pass true for the last block hmac.ComputeMACBlock(lastPart,true); //The MACValue property holds the MAC value Console.WriteLine(hmac.MACValue);

Config Method (HMAC Class)

Sets or retrieves a configuration setting.

Syntax

public String config(String 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.

Reset Method (HMAC Class)

Resets the class.

Syntax

public void reset();

Remarks

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

SetInputStream Method (HMAC Class)

Sets the stream from which the class will read data.

Syntax

public void setInputStream(java.io.InputStream inputStream);

Remarks

This method sets the stream from which the class will read data.

Input Notes

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

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

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops.

Error Event (HMAC Class)

Fired when information is available about errors during data delivery.

Syntax

public class DefaultHMACEventListener implements HMACEventListener {
  ...
  public void error(HMACErrorEvent e) {}
  ...
}

public class HMACErrorEvent {
  public int errorCode;
  public String description;
}

Remarks

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

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 (HMAC Class)

Fired as progress is made.

Syntax

public class DefaultHMACEventListener implements HMACEventListener {
  ...
  public void progress(HMACProgressEvent e) {}
  ...
}

public class HMACProgressEvent {
  public long bytesProcessed;
  public 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 (HMAC Class)

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.

HMAC Config Settings

Base Config Settings

Trappable Errors (HMAC Class)

HMAC Errors