message
Enum ChannelEstablishMessagePart

java.lang.Object
  java.lang.Enum<ChannelEstablishMessagePart>
      message.ChannelEstablishMessagePart

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<ChannelEstablishMessagePart>

public enum ChannelEstablishMessagePart
extends java.lang.Enum<ChannelEstablishMessagePart>

Defines the message format/message parts of a ChannelEstablishMessage. Common message parts are for example "session key" and "payload". The entire message format can be specified within the enum fields. Any ChannelEstablishMessagePart can be retrieved or manipulated using the methods getPart(ChannelEstablishMessagePart messagePart) and setPart(ChannelEstablishMessagePart messagePart, byte[] data) in class ChannelEstablishMessage.

Overlapping message parts are supported (e. g. a field "asymmetric part", which consists of several message parts itself). If a ChannelEstablishMessagePart is of dynamic length (= its length depends on the current mix' position in the cascade (Note: Message length isn't constant in a cascade)), the correct length is calculated automatically.

Note: A MessagePart is "dynamic", when its start and/or end position (=index) is/are equal to, or behind the end position of the last mix' payload (since the payload's size differs from mix to mix (and therefore is a dynamic part as well)).

Each MessagePart provides the following information: It's start offset (= index), it's end offset and whether the part is "part of the header" or not. A MessagePart is considered a "part of the header", when it is exclusive for each mix of the cascade and therefore will be dropped by the corresponding mix. For example a "session key" is "part of the header", since it must be different for each mix and secret to all others (and therefore won't be sent forward). In contrast, the "payload" is not "part of the header", since it is sent from one mix to another (after recoding). Overlapping message parts can't be headers, of course.

See Enum Types Tutorial for information on how to use enumerations in Java.

Note: This enumeration contains the field "MESSAGE_ID" which makes messages TRACEABLE (for debugging)!

Author:

Karl-Peter Fuchs

See Also:

Message

Enum Constant Summary

ASYMMETRIC_PART
The asymmetrically encrypted part of the message.

LEADING_ZERO
Leading zero due to (plain) RSA (first bit must be zero).

MAC
The Message Authentication Code (MAC) of this message.

MAC_KEY
Key used to generate Message Authentication Code (MAC).

MESSAGE_ID
Note: For testing only (MAKES MIX INSECURE): An identifieing number, which is the same for every envelope of a mix message.

PAYLOAD
The payload.

RESERVED
Reserved space (used to fill up header's size to a multiple of the block size).

SESSION_IV
Initialization vector used to decrypt the symmetrically encryptet message part.

SESSION_KEY
Key used to decrypt the symmetrically encrypted message part.

SIGNED_DATA
The signed data of this message.

SYMMETRIC_PART
The symmetrically encrypted part of the message.

TIMESTAMP
Point of time, the message was created.

Method Summary

int	getBasicLength() Returns the "basic" length of this MessagePart in byte.
int	getEndPosition(int numberOfFurtherHops) Returns this MessagePart's (possibly dynamic) end position (= offset), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass).
static int	getHeaderLength() Returns the length of a Message's header as defined above (see static initializer) in byte.
int	getLength(int numberOfFurtherHops) Returns the length of this (possibly dynamic) MessagePart (in byte), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass).
static int	getMessageLength(int numberOfFurtherHops) Returns the (dynamic) length of a mix message, according to the specified mix position in the cascade (in byte).
int	getStartPosition(int numberOfFurtherHops) Returns this MessagePart's (possibly dynamic) start position (= offset), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass).
static ChannelEstablishMessagePart	valueOf(java.lang.String name) Returns the enum constant of this type with the specified name.
static ChannelEstablishMessagePart[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

LEADING_ZERO

public static final ChannelEstablishMessagePart LEADING_ZERO

Leading zero due to (plain) RSA (first bit must be zero). (The other 7 bits of the first byte are not used in this implementation due to readability issues).

MAC

public static final ChannelEstablishMessagePart MAC

The Message Authentication Code (MAC) of this message.

MESSAGE_ID

public static final ChannelEstablishMessagePart MESSAGE_ID

Note: For testing only (MAKES MIX INSECURE): An identifieing number, which is the same for every envelope of a mix message. Used to trace messages for debugging. Can (as all other header-field) only be read correctly, when current envelope is decrypted!

MAC_KEY

public static final ChannelEstablishMessagePart MAC_KEY

Key used to generate Message Authentication Code (MAC).

SESSION_KEY

public static final ChannelEstablishMessagePart SESSION_KEY

Key used to decrypt the symmetrically encrypted message part.

SESSION_IV

public static final ChannelEstablishMessagePart SESSION_IV

Initialization vector used to decrypt the symmetrically encryptet message part.

TIMESTAMP

public static final ChannelEstablishMessagePart TIMESTAMP

Point of time, the message was created.

RESERVED

public static final ChannelEstablishMessagePart RESERVED

Reserved space (used to fill up header's size to a multiple of the block size).

PAYLOAD

public static final ChannelEstablishMessagePart PAYLOAD

The payload.

See Also:

Payload

SIGNED_DATA

public static final ChannelEstablishMessagePart SIGNED_DATA

The signed data of this message.

ASYMMETRIC_PART

public static final ChannelEstablishMessagePart ASYMMETRIC_PART

The asymmetrically encrypted part of the message.

SYMMETRIC_PART

public static final ChannelEstablishMessagePart SYMMETRIC_PART

The symmetrically encrypted part of the message.

Method Detail

values

public static ChannelEstablishMessagePart[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (ChannelEstablishMessagePart c : ChannelEstablishMessagePart.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static ChannelEstablishMessagePart valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

getStartPosition

public int getStartPosition(int numberOfFurtherHops)

Returns this MessagePart's (possibly dynamic) start position (= offset), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Note: Every further hop needs it's own header. Therefore, the message size is not constant.

Parameters:

numberOfFurtherHops - The number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Returns:

This MessagePart's start position (= offset).

getEndPosition

public int getEndPosition(int numberOfFurtherHops)

Returns this MessagePart's (possibly dynamic) end position (= offset), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Note: Every further hop needs it's own header. Therefore, the message size is not constant.

Parameters:

numberOfFurtherHops - The number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Returns:

This MessagePart's end position (= offset).

getLength

public int getLength(int numberOfFurtherHops)

Returns the length of this (possibly dynamic) MessagePart (in byte), according to the number of further hops (=number of mixes this MessagePart's Message still must come to pass). Note: Every further hop needs it's own header. Therefore, the message size is not constant.

Parameters:

numberOfFurtherHops - The number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Returns:

The length of this MessagePart in byte.

getBasicLength

public int getBasicLength()

Returns the "basic" length of this MessagePart in byte. "Basic" means, the length is only valid for the last mix of a cascade.

Returns:

The "basic" length of this MessagePart in byte.

getMessageLength

public static int getMessageLength(int numberOfFurtherHops)

Returns the (dynamic) length of a mix message, according to the specified mix position in the cascade (in byte). (Note: there's no fixed message length in a cascade).

Parameters:

numberOfFurtherHops - The number of further hops (=number of mixes this MessagePart's Message still must come to pass).

Returns:

The (dynamic) length of a mix message for the specified mix position in the cascade.

getHeaderLength

public static int getHeaderLength()

Returns the length of a Message's header as defined above (see static initializer) in byte. Used as incrementation factor to calculate a calling mix' message length according to it's position in the cascade (Note: there's no fixed message length in a cascade).

Returns:

The length of a Message's header (in byte).