RouterKeyGenerator (Javadocs [I2P+ 2.13.0+]

java.lang.Object
- net.i2p.data.RoutingKeyGenerator
- - net.i2p.data.router.RouterKeyGenerator

```
public class RouterKeyGenerator
extends RoutingKeyGenerator
```
Generates routing keys from hashes using date-based modification to prevent Sybil attacks. Transforms input hashes by appending current GMT date (yyyyMMdd format) and computing SHA256. The modification data changes daily at midnight GMT to randomize routing keys consistently. The transformation takes the original hash, appends the bytes of the current mod data, then returns the SHA256 of that concatenation. This makes Sybil attacks much harder as she needs to essentially take over the whole keyspace. Note: generateDateBasedModData() should be called after midnight GMT once per day to generate the correct routing keys.

Constructor Summary
Constructors
Constructor and Description
RouterKeyGenerator(I2PAppContext context)
Constructor that initializes GMT date formatter and generates current routing key modifier data.

Constructors
Constructor and Description
`RouterKeyGenerator(I2PAppContext context)` Constructor that initializes GMT date formatter and generates current routing key modifier data.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`generateDateBasedModData()` Update the current modifier data with some bytes derived from the current date (yyyyMMdd in GMT)
`long`	`getLastChanged()` Time the routing key modifier data was last regenerated.
`byte[]`	`getModData()` The current (today's) mod data.
`byte[]`	`getNextModData()` Tomorrow's mod data.
`Hash`	`getNextRoutingKey(Hash origKey)` Get the routing key using tomorrow's modData, not today's
`Hash`	`getRoutingKey(Hash origKey)` Generate a modified (yet consistent) hash from the origKey by generating the SHA256 of the targetKey with the current modData appended to it This makes Sybil's job a lot harder, as she needs to essentially take over the whole keyspace.
`Hash`	`getRoutingKey(Hash origKey, long time)` Get the routing key for the specified date, not today's
`long`	`getTimeTillMidnight()` How long until midnight (ms)
`static void`	`main(String[] args)`

Methods inherited from class net.i2p.data.RoutingKeyGenerator
getInstance

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

- Constructor Detail
  - RouterKeyGenerator
```
public RouterKeyGenerator(I2PAppContext context)
```
    Constructor that initializes GMT date formatter and generates current routing key modifier data.
- Method Detail
  - generateDateBasedModData
```
public boolean generateDateBasedModData()
```
    Update the current modifier data with some bytes derived from the current date (yyyyMMdd in GMT)
    Returns:
    true if changed
  - getLastChanged
```
public long getLastChanged()
```
    Time the routing key modifier data was last regenerated.
    Specified by:
    getLastChanged in class RoutingKeyGenerator
    Returns:
    the last changed
  - getModData
```
public byte[] getModData()
```
    The current (today's) mod data. Warning - not a copy, do not corrupt.
    Returns:
    non-null, 8 bytes
  - getNextModData
```
public byte[] getNextModData()
```
    Tomorrow's mod data. Warning - not a copy, do not corrupt. For debugging use only.
    Returns:
    non-null, 8 bytes
  - getNextRoutingKey
```
public Hash getNextRoutingKey(Hash origKey)
```
    Get the routing key using tomorrow's modData, not today's
    Returns:
    the next routing key
  - getRoutingKey
```
public Hash getRoutingKey(Hash origKey)
```
    Generate a modified (yet consistent) hash from the origKey by generating the SHA256 of the targetKey with the current modData appended to it This makes Sybil's job a lot harder, as she needs to essentially take over the whole keyspace.
    Specified by:
    getRoutingKey in class RoutingKeyGenerator
    Returns:
    the routing key
    Throws:
    IllegalArgumentException - if origKey is null
  - getRoutingKey
```
public Hash getRoutingKey(Hash origKey,
                          long time)
```
    Get the routing key for the specified date, not today's
    Parameters:
    time - Java time
    Returns:
    the routing key
  - getTimeTillMidnight
```
public long getTimeTillMidnight()
```
    How long until midnight (ms)
    Returns:
    could be slightly negative
  - main
```
public static void main(String[] args)
```

Class RouterKeyGenerator

Constructor Summary

Method Summary

Methods inherited from class net.i2p.data.RoutingKeyGenerator

Methods inherited from class java.lang.Object

Constructor Detail

RouterKeyGenerator

Method Detail

generateDateBasedModData

getLastChanged

getModData

getNextModData

getNextRoutingKey

getRoutingKey

getRoutingKey

getTimeTillMidnight

main