org.bitcoinj.crypto

Class KeyCrypterScrypt

java.lang.Object

org.bitcoinj.crypto.KeyCrypterScrypt

All Implemented Interfaces:

Serializable, KeyCrypter

public class KeyCrypterScrypt
extends Object
implements KeyCrypter

This class encrypts and decrypts byte arrays and strings using scrypt as the key derivation function and AES for the encryption.

You can use this class to:

1) Using a user password, create an AES key that can encrypt and decrypt your private keys. To convert the password to the AES key, scrypt is used. This is an algorithm resistant to brute force attacks. You can use the ScryptParameters to tune how difficult you want this to be generation to be.

2) Using the AES Key generated above, you then can encrypt and decrypt any bytes using the AES symmetric cipher. Eight bytes of salt is used to prevent dictionary attacks.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	BLOCK_LENGTH The size of an AES block in bytes.
static int	KEY_LENGTH Key length in bytes.
static int	SALT_LENGTH The length of the salt used.

Constructor Summary

Constructors

Constructor and Description
KeyCrypterScrypt() Encryption/Decryption using default parameters and a random salt.
KeyCrypterScrypt(int iterations) Encryption/Decryption using custom number of iterations parameters and a random salt.
KeyCrypterScrypt(Protos.ScryptParameters scryptParameters) Encryption/ Decryption using specified Scrypt parameters.

Method Summary

Modifier and Type	Method and Description
byte[]	decrypt(EncryptedData dataToDecrypt, org.spongycastle.crypto.params.KeyParameter aesKey) Decrypt bytes previously encrypted with this class.
org.spongycastle.crypto.params.KeyParameter	deriveKey(CharSequence password) Generate AES key.
EncryptedData	encrypt(byte[] plainBytes, org.spongycastle.crypto.params.KeyParameter aesKey) Password based encryption using AES - CBC 256 bits.
boolean	equals(Object o)
Protos.ScryptParameters	getScryptParameters()
Protos.Wallet.EncryptionType	getUnderstoodEncryptionType() Return the EncryptionType enum value which denotes the type of encryption/ decryption that this KeyCrypter can understand.
int	hashCode()
static byte[]	randomSalt() Returns SALT_LENGTH (8) bytes of random data
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

KEY_LENGTH

public static final int KEY_LENGTH

Key length in bytes.

See Also:

Constant Field Values

BLOCK_LENGTH

public static final int BLOCK_LENGTH

The size of an AES block in bytes. This is also the length of the initialisation vector.

See Also:

Constant Field Values

SALT_LENGTH

public static final int SALT_LENGTH

The length of the salt used.

See Also:

Constant Field Values

Constructor Detail

KeyCrypterScrypt

public KeyCrypterScrypt()

Encryption/Decryption using default parameters and a random salt.

KeyCrypterScrypt

public KeyCrypterScrypt(int iterations)

Encryption/Decryption using custom number of iterations parameters and a random salt. A useful value for mobile devices is 512 (~500 ms).

Parameters:

iterations - number of scrypt iterations

KeyCrypterScrypt

public KeyCrypterScrypt(Protos.ScryptParameters scryptParameters)

Encryption/ Decryption using specified Scrypt parameters.

Parameters:

scryptParameters - ScryptParameters to use

Throws:

NullPointerException - if the scryptParameters or any of its N, R or P is null.

Method Detail

randomSalt

public static byte[] randomSalt()

Returns SALT_LENGTH (8) bytes of random data

deriveKey

public org.spongycastle.crypto.params.KeyParameter deriveKey(CharSequence password)
                                                      throws KeyCrypterException

Generate AES key. This is a very slow operation compared to encrypt/ decrypt so it is normally worth caching the result.

Specified by:

deriveKey in interface KeyCrypter

Parameters:

password - The password to use in key generation

Returns:

The KeyParameter containing the created AES key

Throws:

KeyCrypterException

encrypt

public EncryptedData encrypt(byte[] plainBytes,
                             org.spongycastle.crypto.params.KeyParameter aesKey)
                      throws KeyCrypterException

Password based encryption using AES - CBC 256 bits.

Specified by:

encrypt in interface KeyCrypter

Returns:

encryptedPrivateKey An encryptedPrivateKey containing the encrypted bytes and an initialisation vector.

Throws:

KeyCrypterException - if encryption was unsuccessful

decrypt

public byte[] decrypt(EncryptedData dataToDecrypt,
                      org.spongycastle.crypto.params.KeyParameter aesKey)
               throws KeyCrypterException

Decrypt bytes previously encrypted with this class.

Specified by:

decrypt in interface KeyCrypter

Parameters:

dataToDecrypt - The data to decrypt

aesKey - The AES key to use for decryption

Returns:

The decrypted bytes

Throws:

KeyCrypterException - if bytes could not be decrypted

getScryptParameters

public Protos.ScryptParameters getScryptParameters()

getUnderstoodEncryptionType

public Protos.Wallet.EncryptionType getUnderstoodEncryptionType()

Return the EncryptionType enum value which denotes the type of encryption/ decryption that this KeyCrypter can understand.

Specified by:

getUnderstoodEncryptionType in interface KeyCrypter

toString

public String toString()

Overrides:

toString in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object