HMACGenerator (Javadocs [I2P+ 2.13.0+]

java.lang.Object
- net.i2p.crypto.HMACGenerator

Direct Known Subclasses:
HMAC256Generator
```
public abstract class HMACGenerator
extends Object
```
Abstract base class for HMAC (Hash-based Message Authentication Code) operations. This class provides the foundation for HMAC algorithm implementations used throughout I2P for message authentication and integrity verification. It defines the standard interface for calculating and verifying HMAC values with various hash algorithms.
Key operations include:
- HMAC calculation with given key and message data
- Inline MAC verification for performance optimization
- Support for different hash algorithms (SHA-1, SHA-256)
- Integration with I2P's session key management
Implementation Note: As of 0.9.42, this class serves as an abstract base. See net.i2p.router.transport.udp.SSUHMACGenerator for SSU-specific HMAC implementation and SHA256Generator for Syndie-compatible HMAC operations.

Constructor Summary
Constructors
Constructor and Description
HMACGenerator()
HMACGenerator.

Constructors
Constructor and Description
`HMACGenerator()` HMACGenerator.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`protected byte[]`	`acquireTmp()` 32 bytes from the byte array cache.
`abstract void`	`calculate(SessionKey key, byte[] data, int offset, int length, byte[] target, int targetOffset)` Calculate the HMAC of the data with the given key
`protected void`	`releaseTmp(byte[] tmp)` releaseTmp.
`abstract boolean`	`verify(SessionKey key, byte[] curData, int curOffset, int curLength, byte[] origMAC, int origMACOffset, int origMACLength)` Verify the MAC inline, reducing some unnecessary memory churn.

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

- Constructor Detail
  - HMACGenerator
```
public HMACGenerator()
```
    HMACGenerator.
- Method Detail
  - acquireTmp
```
protected byte[] acquireTmp()
```
    32 bytes from the byte array cache. Does NOT zero.
    Returns:
    32-byte tmp array
  - calculate
```
public abstract void calculate(SessionKey key,
                               byte[] data,
                               int offset,
                               int length,
                               byte[] target,
                               int targetOffset)
```
    Calculate the HMAC of the data with the given key
    Parameters:
    key - the session key
    data - the data to HMAC
    offset - the starting offset in data
    length - the length
    target - out parameter the first 16 bytes contain the HMAC, the last 16 bytes are zero
    targetOffset - offset into target to put the hmac
    Throws:
    IllegalArgumentException - for bad key or target too small
  - releaseTmp
```
protected void releaseTmp(byte[] tmp)
```
    releaseTmp.
  - verify
```
public abstract boolean verify(SessionKey key,
                               byte[] curData,
                               int curOffset,
                               int curLength,
                               byte[] origMAC,
                               int origMACOffset,
                               int origMACLength)
```
    Verify the MAC inline, reducing some unnecessary memory churn.
    Parameters:
    key - session key to verify the MAC with
    curData - MAC to verify
    curOffset - index into curData to MAC
    curLength - how much data in curData do we want to run the HMAC over
    origMAC - what do we expect the MAC of curData to equal
    origMACOffset - index into origMAC
    origMACLength - how much of the MAC do we want to verify
    Returns:
    true if the MAC matches
    Throws:
    IllegalArgumentException - for bad key

Class HMACGenerator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

HMACGenerator

Method Detail

acquireTmp

calculate

releaseTmp

verify