net.i2p.data

Class Signature

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 40

Fields inherited from class net.i2p.data.SimpleDataStructure

_data

Constructor Summary

Constructors

Constructor and Description
Signature()
Signature(byte[] data)
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

Modifier and Type	Method and Description
boolean	equals(Object obj) Warning - this returns true for two different classes with the same size and same data, e.g.
SigType	getType() Gets the signature type.
int	hashCode() We assume the data has enough randomness in it, so use the first 4 bytes for speed.
int	length() The legal length of the byte array in this data structure
String	toString()

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

40

Constructor Detail

Signature

public Signature()

Signature

public Signature(byte[] data)

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

Method Detail

equals

public boolean equals(Object obj)

Description copied from class: SimpleDataStructure

Warning - this returns true for two different classes with the same size and same data, e.g. SessionKey and SessionTag, but you wouldn't put them in the same Set, would you?

Overrides:

equals in class SimpleDataStructure

getType

public SigType getType()

Gets the signature type.

Returns:

non-null

hashCode

public int hashCode()

Description copied from class: SimpleDataStructure

We assume the data has enough randomness in it, so use the first 4 bytes for speed. If this is not the case, override in the extending class.

Overrides:

hashCode in class SimpleDataStructure

length

public int length()

Description copied from class: SimpleDataStructure

The legal length of the byte array in this data structure

Specified by:

length in class SimpleDataStructure

toString

public String toString()

Overrides:

toString in class SimpleDataStructure