Signature (Javadocs [I2P+ 2.13.0+] - API Version 0.9.70+)

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

All Implemented Interfaces:
DataStructure
```
public class Signature
extends SimpleDataStructure
```
Cryptographic signature implementation for I2P data structures and identity verification.
Signature provides digital signature capabilities with support for multiple algorithms:
- Default Algorithm: DSA-SHA1 (40 bytes: 20-byte R + 20-byte S)
- Modern Algorithms: ECDSA-P256, EdDSA-Ed25519 with variable lengths
- Algorithm Support: Extensible design for future signature types
- Verification: Used throughout I2P for identity and data integrity
Signature Structure:
- DSA-SHA1: 40 bytes total (R: 20 bytes, S: 20 bytes)
- ECDSA-P256: Variable length (typically 64-72 bytes)
- EdDSA-Ed25519: 64 bytes (fixed length)
- Type Information: Embedded in signature data for verification
Supported Algorithms:
- DSA-SHA1: Legacy algorithm, 1024-bit keys
- ECDSA-P256: Modern algorithm, 256-bit elliptic curve
- EdDSA-Ed25519: Modern algorithm, 25519 elliptic curve
- RSA: Supported but discouraged due to performance issues
Usage:
- Identity Verification: Proves ownership of Destination
- Data Integrity: Ensures data hasn't been tampered with
- NetDb Entries: Signs RouterInfo and LeaseSet structures
- Messages: Authenticates I2NP messages and I2CP communications
Security Considerations:
- Algorithm Selection: Prefer modern algorithms (Ed25519, ECDSA-P256)
- Key Management: Protect private signing keys
- Verification: Always verify signatures before trusting data
- Performance: RSA signatures are slow and may be used for DoS
Evolution:
- Pre-0.9.8: Only DSA-SHA1 supported (40 bytes fixed)
- Post-0.9.8: Arbitrary length and type support via SigType
- Current: Multiple algorithms with automatic type detection

Field Summary
Fields
Modifier and Type Field and Description
static int SIGNATURE_BYTES
Default signature length in bytes.
- Fields inherited from class net.i2p.data.SimpleDataStructure
  _data

Fields
Modifier and Type	Field and Description
`static int`	`SIGNATURE_BYTES` Default signature length in bytes.

Constructor Summary

Constructors
Constructor and Description
`Signature()` Creates a new Signature with the default DSA-SHA1 type.
`Signature(byte[] data)` Creates a new Signature from byte data with default type.
`Signature(SigType type)` Unknown type not allowed as we won't know the length to read in the data.
`Signature(SigType type, byte[] data)` Should we allow an unknown type here?

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`equals(Object obj)` Compares this signature with another object for equality.
`SigType`	`getType()` Gets the signature type.
`int`	`hashCode()` Hash code combining the type and data.
`int`	`length()` Signature length in bytes, determined by the signature type.
`String`	`toString()` Returns a string representation of this data structure.

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

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

- Field Detail
  - SIGNATURE_BYTES
```
public static final int SIGNATURE_BYTES
```
    Default signature length in bytes.
- Constructor Detail
  - Signature
```
public Signature()
```
    Creates a new Signature with the default DSA-SHA1 type.
  - Signature
```
public Signature(byte[] data)
```
    Creates a new Signature from byte data with default type.
  - Signature
```
public Signature(SigType type)
```
    Unknown type not allowed as we won't know the length to read in the data.
    Parameters:
    type - non-null
  - Signature
```
public Signature(SigType type,
                 byte[] data)
```
    Should we allow an unknown type here?
    Parameters:
    type - non-null
    data - the signature data
- Method Detail
  - equals
```
public boolean equals(Object obj)
```
    Compares this signature with another object for equality.
    Overrides:
    equals in class SimpleDataStructure
    Parameters:
    obj - the object to compare
    Returns:
    true if equal
  - getType
```
public SigType getType()
```
    Gets the signature type.
    Returns:
    non-null
  - hashCode
```
public int hashCode()
```
    Hash code combining the type and data.
    Overrides:
    hashCode in class SimpleDataStructure
    Returns:
    the hash code
  - length
```
public int length()
```
    Signature length in bytes, determined by the signature type.
    Specified by:
    length in class SimpleDataStructure
    Returns:
    the legal length of the byte array
  - toString
```
public String toString()
```
    Description copied from class: SimpleDataStructure
    Returns a string representation of this data structure.
    Overrides:
    toString in class SimpleDataStructure

Class Signature

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

SIGNATURE_BYTES

Constructor Detail

Signature

Signature

Signature

Signature

Method Detail

equals

getType

hashCode

length

toString