SigningPublicKey (Javadocs [I2P+ 2.13.0+]

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

All Implemented Interfaces:
DataStructure
```
public class SigningPublicKey
extends SimpleDataStructure
```
Cryptographic public key for digital signature verification in I2P.
SigningPublicKey provides signature verification capabilities:
- Default Algorithm: DSA-SHA1 (128 bytes)
- Modern Support: Variable length and type support since 0.9.8
- Key Structure: Contains only public exponent/coordinates
- Verification: Used to verify signatures and identities
Supported Algorithms:
- DSA-SHA1: Legacy algorithm, 128-byte keys
- ECDSA-P256: Modern algorithm, variable length keys
- EdDSA-Ed25519: Modern algorithm, 32-byte keys
- Future Types: Extensible design for new algorithms
Key Format:
- DSA: 128-byte public parameters (p, q, g, y)
- ECDSA: Variable length elliptic curve coordinates
- EdDSA: 32-byte compressed curve point
- Type Encoding: Algorithm type embedded in data
Usage:
- Signature Verification: Verify signatures from SigningPrivateKey
- Identity Verification: Part of Destination identity
- LeaseSet Verification: Verify LeaseSet authenticity
- Router Identity: Verify router signatures in NetDb
Performance Features:
- LRU Caching: Frequently used keys cached for efficiency
- Factory Methods: Static creation methods for cache access
- Efficient Storage: Optimized byte representation
- Fast Comparison: Optimized equals() and hashCode()
Security Considerations:
- Algorithm Choice: Prefer modern algorithms (Ed25519, ECDSA-P256)
- Key Validation: Verify key parameters before use
- Signature Verification: Always verify with correct algorithm
- Key Distribution: Safely transmit public keys
Blinding Support:
- Key Blinding: Support for blinded key variants
- Privacy: Enable anonymous service endpoints
- BlindData: Integration with BlindData for blinding
Migration Path:
- Legacy: DSA-SHA1 for backward compatibility
- Modern: Ed25519 for better performance and security
- Transition: Mixed algorithm support during migration
Thread Safety:
- Immutable Data: Key data cannot be modified after creation
- Thread-Safe Cache: Static factory methods are thread-safe
- Safe Sharing: Instances can be safely shared between threads

Field Summary
Fields
Modifier and Type Field and Description
static int KEYSIZE_BYTES
Default key size in bytes (128 for DSA-SHA1).
- Fields inherited from class net.i2p.data.SimpleDataStructure
  _data

Fields
Modifier and Type	Field and Description
`static int`	`KEYSIZE_BYTES` Default key size in bytes (128 for DSA-SHA1).

Constructor Summary

Constructors
Constructor and Description
`SigningPublicKey()` Creates a new SigningPublicKey with the default DSA-SHA1 type.
`SigningPublicKey(byte[] data)` Creates a new SigningPublicKey from byte data with default type.
`SigningPublicKey(SigType type)` If null, type is unknown.
`SigningPublicKey(SigType type, byte[] data)` If null, type is unknown.
`SigningPublicKey(String base64Data)` constructs from base64

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`SigningPublicKey`	`blind(SigningPrivateKey alpha)` Only for SigType EdDSA_SHA512_Ed25519
`static void`	`clearCache()` Clears the public key cache.
`static SigningPublicKey`	`create(byte[] data, int off)` Pull from cache or return new.
`static SigningPublicKey`	`create(InputStream in)` Pull from cache or return new
`boolean`	`equals(Object obj)` Warning - this returns true for two different classes with the same size and same data, e.g.
`byte[]`	`getPadding(KeyCertificate kcert)` Get the portion of this (type 0) SPK that is really padding based on the Key Cert type given, if any
`SigType`	`getType()` Gets the signature type of this public key.
`int`	`hashCode()` Hash code combining the type and data.
`int`	`length()` If type unknown, the length of the data, or 128 if no data.
`String`	`toString()` Returns a string representation of this data structure.
`(package private) SigningPublicKey`	`toTypedKey(KeyCertificate kcert)` Up-convert this from an untyped (type 0) SPK to a typed SPK based on the Key Cert given.
`(package private) void`	`writeTruncatedBytes(OutputStream out)` Write the data up to a max of 128 bytes.

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
  - KEYSIZE_BYTES
```
public static final int KEYSIZE_BYTES
```
    Default key size in bytes (128 for DSA-SHA1).
- Constructor Detail
  - SigningPublicKey
```
public SigningPublicKey()
```
    Creates a new SigningPublicKey with the default DSA-SHA1 type.
  - SigningPublicKey
```
public SigningPublicKey(byte[] data)
```
    Creates a new SigningPublicKey from byte data with default type.
  - SigningPublicKey
```
public SigningPublicKey(SigType type)
```
    If null, type is unknown.
    Parameters:
    type - if null, type is unknown
  - SigningPublicKey
```
public SigningPublicKey(SigType type,
                        byte[] data)
```
    If null, type is unknown.
    Parameters:
    type - if null, type is unknown
    data - the key data
  - SigningPublicKey
```
public SigningPublicKey(String base64Data)
                 throws DataFormatException
```
    constructs from base64
    Parameters:
    base64Data - a string of base64 data (the output of .toBase64() called on a prior instance of SigningPublicKey
    Throws:
    DataFormatException
- Method Detail
  - blind
```
public SigningPublicKey blind(SigningPrivateKey alpha)
```
    Only for SigType EdDSA_SHA512_Ed25519
    Parameters:
    alpha - the secret data
    Returns:
    the blinded public key
    Throws:
    UnsupportedOperationException - unless supported
  - clearCache
```
public static void clearCache()
```
    Clears the public key cache.
  - create
```
public static SigningPublicKey create(byte[] data,
                                      int off)
```
    Pull from cache or return new. Deprecated - used only by deprecated Destination.readBytes(data, off)
    Returns:
    the cached or new key
  - create
```
public static SigningPublicKey create(InputStream in)
                               throws IOException
```
    Pull from cache or return new
    Returns:
    the cached or new key
    Throws:
    IOException
  - 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
    Parameters:
    obj - the object to compare
    Returns:
    true if equal
  - getPadding
```
public byte[] getPadding(KeyCertificate kcert)
```
    Get the portion of this (type 0) SPK that is really padding based on the Key Cert type given, if any
    Returns:
    leading padding length > 0 or null if no padding or type is unknown
    Throws:
    IllegalArgumentException - if this is already typed to a different type
  - getType
```
public SigType getType()
```
    Gets the signature type of this public key.
    Returns:
    null if unknown
  - hashCode
```
public int hashCode()
```
    Hash code combining the type and data.
    Overrides:
    hashCode in class SimpleDataStructure
    Returns:
    the hash code
  - length
```
public int length()
```
    If type unknown, the length of the data, or 128 if no data.
    Specified by:
    length in class SimpleDataStructure
    Returns:
    if type unknown, the length of the data, or 128 if no data
  - toString
```
public String toString()
```
    Description copied from class: SimpleDataStructure
    Returns a string representation of this data structure.
    Overrides:
    toString in class SimpleDataStructure
  - toTypedKey
```
SigningPublicKey toTypedKey(KeyCertificate kcert)
```
    Up-convert this from an untyped (type 0) SPK to a typed SPK based on the Key Cert given. The type of the returned key will be null if the kcert sigtype is null.
    Parameters:
    kcert - the key certificate
    Returns:
    the typed signing public key
    Throws:
    IllegalArgumentException - if this is already typed to a different type
  - writeTruncatedBytes
```
void writeTruncatedBytes(OutputStream out)
                  throws DataFormatException,
                         IOException
```
    Write the data up to a max of 128 bytes. If longer, the rest will be written in the KeyCertificate.
    Throws:
    DataFormatException
    IOException

Class SigningPublicKey

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

KEYSIZE_BYTES

Constructor Detail

SigningPublicKey

SigningPublicKey

SigningPublicKey

SigningPublicKey

SigningPublicKey

Method Detail

blind

clearCache

create

create

equals

getPadding

getType

hashCode

length

toString

toTypedKey

writeTruncatedBytes