net.i2p.crypto

Class SigContext.SigContextSpec

java.lang.Object

net.i2p.crypto.SigContext.SigContextSpec

All Implemented Interfaces:

AlgorithmParameterSpec

Enclosing class:

SigContext

public static class SigContext.SigContextSpec
extends Object
implements AlgorithmParameterSpec

Algorithm parameter specification for personalized hash contexts in digital signatures. This class implements AlgorithmParameterSpec to provide context-specific data for cryptographic signature operations using personalized hash functions. The context data is used as domain separation to prevent signature replay attacks across different I2P protocols and data types.

Purpose and Security:

• Domain separation between different I2P protocols
• Prevention of cross-protocol signature replay attacks
• Implementation of Proposal 148 for enhanced signature security
• Context-specific hash personalization for BLAKE signature engines

Format and Validation:

• Context data must be exactly 16 ASCII bytes
• Null context indicates no personalization (SC_NONE)
• Invalid lengths throw IllegalArgumentException
• Data is stored as raw bytes for cryptographic operations

Usage:

 // Get context specification for datagram signatures
 SigContextSpec spec = SigContext.SC_DATAGRAM.getSpec();
 
 // Apply to signature engine
 signatureEngine.setParameter(spec);
 

Supported Contexts:

• SC_DATAGRAM - Datagram protocol signatures
• SC_I2CP - I2CP session configuration
• SC_NETDB - Network database entries
• SC_NTCP - NTCP handshake signatures
• SC_SSU - SSU handshake signatures
• SC_STREAMING - Streaming protocol signatures
• SC_SU3 - SU3 file format signatures
• SC_TEST - Test context for development

Thread Safety: This class is immutable and thread-safe. The returned byte array should not be modified by callers.

See Also:

AlgorithmParameterSpec, SigContext

Constructor Summary

Constructors

Constructor and Description
SigContextSpec(String context) Creates a signature context specification from the given context string.

Method Summary

Modifier and Type	Method and Description
byte[]	getData() Returns the raw context data for cryptographic operations.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SigContextSpec

public SigContextSpec(String context)

Creates a signature context specification from the given context string.

Parameters:

context - the ASCII context string, must be exactly 16 characters, or null for no context (SC_NONE)

Throws:

IllegalArgumentException - if the context string is not exactly 16 characters

Method Detail

getData

public byte[] getData()

Returns the raw context data for cryptographic operations. The returned array is the internal storage and should not be modified.

Returns:

the 16-byte context data as a byte array, or null if no context is set