SessionKey (Javadocs [I2P+ 2.13.0+]

java.lang.Object
- net.i2p.data.SimpleDataStructure
- - net.i2p.data.SessionKey

All Implemented Interfaces:
DataStructure
Direct Known Subclasses:
SessionKeyAndNonce
```
public class SessionKey
extends SimpleDataStructure
```
Cryptographic session key for symmetric encryption in I2P.
SessionKey provides symmetric encryption capabilities for I2P communications:
- Fixed Size: 32-byte key suitable for modern symmetric algorithms
- Session-Based: Temporary keys for message encryption/decryption
- Algorithm Agnostic: Can be used with various symmetric ciphers
- Efficient Storage: Optimized for high-frequency operations
Key Generation:
- Random Creation: Use I2PAppContext.keyGenerator().generateSessionKey()
- Cryptographically Secure: Generated using cryptographically strong randomness
- Factory Methods: Static creation methods for convenience
- Invalid Key: Pre-defined all-zero key for special cases
Usage Patterns:
- Message Encryption: Encrypt I2NP messages and I2CP data
- Tunnel Encryption: Protect tunnel payload contents
- Session Establishment: Derive from key exchange protocols
- Temporary Storage: Short-lived keys for enhanced security
Security Considerations:
- Key Protection: Never expose session keys to unauthorized parties
- Secure Generation: Use cryptographically secure random sources
- Key Rotation: Change keys regularly to limit exposure
- Memory Security: Zeroize memory when keys are no longer needed
Performance Features:
- Prepared Keys: Cache for algorithm-specific prepared keys
- Efficient Storage: Optimized byte array representation
- Fast Operations: Quick access and comparison methods
- Memory Management: Careful allocation and cleanup
Integration:
- I2P Client: Used for end-to-end encryption in I2CP
- Router Operations: Tunnel and message encryption
- Garlic Encryption: Multi-layer message protection
- ElGamal Integration: Combined with asymmetric encryption for key exchange
Constants:
- KEYSIZE_BYTES - Standard 32-byte key length
- INVALID_KEY - All-zero key for invalid/placeholder use
Best Practices:
- Unique Sessions: Use different keys for different communication sessions
- Limited Lifetime: Replace keys after reasonable time period
- Secure Disposal: Clear key data when session ends
- Algorithm Selection: Use appropriate symmetric cipher for key size

Field Summary
Fields
Modifier and Type Field and Description
static SessionKey INVALID_KEY
A key with all zeroes in the data
static int KEYSIZE_BYTES
Key size in bytes (32).
- Fields inherited from class net.i2p.data.SimpleDataStructure
  _data

Fields
Modifier and Type	Field and Description
`static SessionKey`	`INVALID_KEY` A key with all zeroes in the data
`static int`	`KEYSIZE_BYTES` Key size in bytes (32).

Constructor Summary
Constructors
Constructor and Description
SessionKey()
SessionKey(byte[] data)
Key data.

Constructors
Constructor and Description
`SessionKey()`
`SessionKey(byte[] data)` Key data.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`getPreparedKey()` retrieve an internal representation of the session key, as known by the AES engine used.
`int`	`length()` The legal length of the byte array in this data structure.
`void`	`setData(byte[] data)` Sets the data.
`void`	`setPreparedKey(Object obj)` Set the internal prepared AES key representation.

Methods inherited from class net.i2p.data.SimpleDataStructure
calculateHash, equals, fromBase64, fromByteArray, getData, hashCode, read, readBytes, toBase64, toByteArray, toString, writeBytes

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - INVALID_KEY
```
public static final SessionKey INVALID_KEY
```
    A key with all zeroes in the data
  - KEYSIZE_BYTES
```
public static final int KEYSIZE_BYTES
```
    Key size in bytes (32).
    See Also:
    Constant Field Values
- Constructor Detail
  - SessionKey
```
public SessionKey()
```
  - SessionKey
```
public SessionKey(byte[] data)
```
    Key data.
    Parameters:
    data - the key data
- Method Detail
  - getPreparedKey
```
public Object getPreparedKey()
```
    retrieve an internal representation of the session key, as known by the AES engine used. this can be reused safely
    Returns:
    the prepared key
  - length
```
public int length()
```
    The legal length of the byte array in this data structure.
    Specified by:
    length in class SimpleDataStructure
    Returns:
    the legal length of the byte array
  - setData
```
public void setData(byte[] data)
```
    Sets the data.
    Overrides:
    setData in class SimpleDataStructure
    Parameters:
    data - 32 bytes, or null
    Throws:
    IllegalArgumentException - if data is not the legal number of bytes (but null is ok)
    RuntimeException - if data already set.
  - setPreparedKey
```
public void setPreparedKey(Object obj)
```
    Set the internal prepared AES key representation.
    Parameters:
    obj - the prepared key object

Class SessionKey

Field Summary

Fields inherited from class net.i2p.data.SimpleDataStructure

Constructor Summary

Method Summary

Methods inherited from class net.i2p.data.SimpleDataStructure

Methods inherited from class java.lang.Object

Field Detail

INVALID_KEY

KEYSIZE_BYTES

Constructor Detail

SessionKey

SessionKey

Method Detail

getPreparedKey

length

setData

setPreparedKey