Destination (Javadocs [I2P+ 2.13.0+]

java.lang.Object
- net.i2p.data.DataStructureImpl
- - net.i2p.data.KeysAndCert
  - - net.i2p.data.Destination

All Implemented Interfaces:
Serializable, DataStructure
Direct Known Subclasses:
VerifiedDestination
```
public class Destination
extends KeysAndCert
```
Defines an endpoint in the I2P network that can receive messages.
Destination represents the fundamental addressing and identity concept in I2P:
- Network Endpoint: Messages sent to a Destination will find it regardless of location
- Cryptographic Identity: Contains encryption and signing keys
- Certificate: Optional metadata about the identity
- Addressing: Can be encoded as Base64 or Base32 (.b32.i2p)
- Immutability: Identity becomes immutable after keys are set
Key Components:
- Public Encryption Key: Historically used for end-to-end encryption
- Signing Public Key: Used for identity verification and LeaseSet signing
- Certificate: Optional metadata (NULL, HIDDEN, SIGNED, etc.)
- Cached Hash: SHA-256 hash for efficient identification
Address Formats:
- Base64: Full binary encoding for configuration files
- Base32: Human-readable .b32.i2p addresses
- Hash: 32-byte SHA-256 for internal identification
Historical Changes:
- Pre-0.6: Public key used for end-to-end encryption
- Post-0.6: End-to-end encryption removed, LeaseSet keys used instead
- LeaseSet Encryption: Public key first bytes used as IV (deprecated)
- 0.9.9: Immutable after keys and certificate are set
Usage:
- Client Connections: Target for I2P client communications
- Service Hosting: Identity for hosting I2P services
- Message Routing: Destination for I2NP message delivery
- Address Book: Entry in address books and contact lists
Security Considerations:
- Key Protection: Private keys must be securely stored
- Identity Verification: Always verify signatures from destinations
- Certificate Validation: Check certificate types and content
- Deprecated Features: Avoid legacy encryption mechanisms
Performance Features:
- Caching: LRU cache for frequently used destinations
- Lazy Computation: Base32 address computed on demand
- Efficient Storage: Optimized memory usage and serialization
- Fast Lookup: Hash-based identification for quick comparisons
Immutability:
- After 0.9.9: Keys and certificate cannot be changed after setting
- Thread Safety: Immutable objects are inherently thread-safe
- Corruption Prevention: Protects against accidental modification
- Exception: Modification attempts throw IllegalStateException
Migration Notes:
- Legacy Encryption: Public key usage deprecated in favor of LeaseSet encryption
- Modern Alternatives: Use EncryptedLeaseSet for proper encryption
- IV Generation: LeaseSet encryption IV should not use public key bytes
See Also:
Serialized Form

Field Summary
- Fields inherited from class net.i2p.data.KeysAndCert
  _certificate, _paddingBlocks, _publicKey, _signingKey

Constructor Summary
Constructors
Constructor and Description
Destination()
Empty destination with no data set.
Destination(String s)
alternative constructor which takes a base64 string representation

Constructors
Constructor and Description
`Destination()` Empty destination with no data set.
`Destination(String s)` alternative constructor which takes a base64 string representation

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static void`	`clearCache()` Clear the cache.
`static Destination`	`create(InputStream in)` Pull from cache or return new
`boolean`	`equals(Object o)` equals.
`int`	`hashCode()` Whether h code is present.
`int`	`size()` Serialized size of this destination.
`String`	`toBase32()` For convenience.
`String`	`toBase64()` Cache it.
`int`	`writeBytes(byte[] target, int offset)` Deprecated, used only by Packet.java in streaming.

Methods inherited from class net.i2p.data.KeysAndCert
calculateHash, combinePadding, getCertificate, getEncType, getHash, getPadding, getPublicKey, getSigningPublicKey, getSigType, isCompressible, readBytes, setCertificate, setPadding, setPublicKey, setSigningPublicKey, toString, writeBytes, writePaddingBytes

Methods inherited from class net.i2p.data.DataStructureImpl
fromBase64, fromByteArray, read, toByteArray

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

- Constructor Detail
  - Destination
```
public Destination()
```
    Empty destination with no data set.
  - Destination
```
public Destination(String s)
            throws DataFormatException
```
    alternative constructor which takes a base64 string representation
    Parameters:
    s - a Base64 representation of the destination, as (eg) is used in hosts.txt
    Throws:
    DataFormatException - if the string is invalid
- Method Detail
  - clearCache
```
public static void clearCache()
```
    Clear the cache.
  - create
```
public static Destination create(InputStream in)
                          throws DataFormatException,
                                 IOException
```
    Pull from cache or return new
    Parameters:
    in - the input stream
    Returns:
    the destination
    Throws:
    DataFormatException - if data is invalid
    IOException - if an I/O error occurs
  - equals
```
public boolean equals(Object o)
```
    equals.
    Overrides:
    equals in class KeysAndCert
  - hashCode
```
public int hashCode()
```
    Whether h code is present.
    Overrides:
    hashCode in class KeysAndCert
    Returns:
    whether h code is present
  - size
```
public int size()
```
    Serialized size of this destination.
    Returns:
    the size in bytes
  - toBase32
```
public String toBase32()
```
    For convenience.
    Returns:
    "{52 chars}.b32.i2p" or null if fields not set.
  - toBase64
```
public String toBase64()
```
    Cache it. Useful in I2PTunnelHTTPServer where it is added to the headers
    Specified by:
    toBase64 in interface DataStructure
    Overrides:
    toBase64 in class DataStructureImpl
    Returns:
    null on error
  - writeBytes
```
public int writeBytes(byte[] target,
                      int offset)
```
    Deprecated, used only by Packet.java in streaming. Broken for sig types P521 and RSA before 0.9.15
    Parameters:
    target - the target
    offset - the offset to start writing
    Returns:
    the written length (NOT the new offset)

Class Destination

Field Summary

Fields inherited from class net.i2p.data.KeysAndCert

Constructor Summary

Method Summary

Methods inherited from class net.i2p.data.KeysAndCert

Methods inherited from class net.i2p.data.DataStructureImpl

Methods inherited from class java.lang.Object

Constructor Detail

Destination

Destination

Method Detail

clearCache

create

equals

hashCode

size

toBase32

toBase64

writeBytes