org.snmp4j.security

Class PrivAES

java.lang.Object

org.snmp4j.security.PrivAES

All Implemented Interfaces:

Serializable, PrivacyProtocol, SecurityProtocol

Direct Known Subclasses:

PrivAES128, PrivAES192, PrivAES256, PrivAESWith3DESKeyExtension

public abstract class PrivAES
extends Object
implements PrivacyProtocol

Base class for PrivAES128, PrivAES192 and PrivAES256. This class uses AES in CFB mode to encrypt the data. The protocol is defined in draft-blumenthal-aes-usm-08.txt (AES128) and draft-blumenthal-aes-usm-04.txt (AES192 and AES256).

Version:

2.2.3

Author:

Jochen Katz

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected CipherPool	cipherPool
protected org.snmp4j.security.Salt	salt

Constructor Summary

Constructors

Constructor and Description
PrivAES(int keyBytes) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
static String	asHex(byte[] buf) Turns array of bytes into string
byte[]	decrypt(byte[] cryptedData, int offset, int length, byte[] decryptionKey, long engineBoots, long engineTime, DecryptParams decryptParams) Decrypts a message using a given decryption key, engine boots count, and engine ID.
byte[]	encrypt(byte[] unencryptedData, int offset, int length, byte[] encryptionKey, long engineBoots, long engineTime, DecryptParams decryptParams) Encrypts a message using a given encryption key, engine boots count, and engine ID.
byte[]	extendShortKey(byte[] shortKey, OctetString password, byte[] engineID, AuthenticationProtocol authProtocol) Extend a localized key that is too short.
int	getDecryptParamsLength() Gets the length of the decryption parameters used by this security protocol.
int	getEncryptedLength(int scopedPDULength) Gets the length of a scoped PDU when encrypted with this security protocol.
int	getMaxKeyLength() Gets the maximum key size for this privacy protcol.
int	getMinKeyLength() Gets the minimum key size for this privacy protcol.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.snmp4j.security.PrivacyProtocol

getID

Field Detail

salt

protected org.snmp4j.security.Salt salt

cipherPool

protected CipherPool cipherPool

Constructor Detail

PrivAES

public PrivAES(int keyBytes)

Constructor.

Parameters:

keyBytes - Length of key, must be 16, 24 or 32.

Throws:

IllegalArgumentException - if keyBytes is illegal

Method Detail

encrypt

public byte[] encrypt(byte[] unencryptedData,
             int offset,
             int length,
             byte[] encryptionKey,
             long engineBoots,
             long engineTime,
             DecryptParams decryptParams)

Description copied from interface: PrivacyProtocol

Encrypts a message using a given encryption key, engine boots count, and engine ID.

Specified by:

encrypt in interface PrivacyProtocol

Parameters:

unencryptedData - the unencrypted data. This byte array may contain leading and trailing bytes that will not be encrypted.

offset - the offset into the unencryptedData where to start encryption.

length - the length of the substring starting at offset to encrypt.

encryptionKey - the key to be used for encryption.

engineBoots - the engine boots counter to use.

engineTime - the engine time to use.

decryptParams - returns the decryption parameters needed to decrypt the data that has been encrypted by this method.

Returns:

the encrypted copy of unencryptedData.

decrypt

public byte[] decrypt(byte[] cryptedData,
             int offset,
             int length,
             byte[] decryptionKey,
             long engineBoots,
             long engineTime,
             DecryptParams decryptParams)

Description copied from interface: PrivacyProtocol

Decrypts a message using a given decryption key, engine boots count, and engine ID.

Specified by:

decrypt in interface PrivacyProtocol

Parameters:

cryptedData - the crypted data. This byte array may contain leading and trailing bytes that will not be decrypted.

offset - the offset into the cryptedData where to start encryption.

length - the length of the substring starting at offset to decrypt.

decryptionKey - the key to be used for decryption.

engineBoots - the engine boots counter to use.

engineTime - the engine time to use.

decryptParams - contains the decryption parameters.

Returns:

the decrypted data, or null if decryption failed.

getEncryptedLength

public int getEncryptedLength(int scopedPDULength)

Description copied from interface: PrivacyProtocol

Gets the length of a scoped PDU when encrypted with this security protocol.

Specified by:

getEncryptedLength in interface PrivacyProtocol

Parameters:

scopedPDULength - the length of the (unencrypted) scoped PDU.

Returns:

the length of the encrypted scoped PDU.

asHex

public static String asHex(byte[] buf)

Turns array of bytes into string

Parameters:

buf - Array of bytes to convert to hex string

Returns:

Generated hex string

getMinKeyLength

public int getMinKeyLength()

Description copied from interface: PrivacyProtocol

Gets the minimum key size for this privacy protcol.

Specified by:

getMinKeyLength in interface PrivacyProtocol

Returns:

the minimum key size for this privacy protcol.

getMaxKeyLength

public int getMaxKeyLength()

Description copied from interface: PrivacyProtocol

Gets the maximum key size for this privacy protcol.

Specified by:

getMaxKeyLength in interface PrivacyProtocol

Returns:

the minimum key size for this privacy protcol.

getDecryptParamsLength

public int getDecryptParamsLength()

Description copied from interface: PrivacyProtocol

Gets the length of the decryption parameters used by this security protocol.

Specified by:

getDecryptParamsLength in interface PrivacyProtocol

Returns:

a positive integer denoting the length of decryption parameters returned by this security protocol.

extendShortKey

public byte[] extendShortKey(byte[] shortKey,
                    OctetString password,
                    byte[] engineID,
                    AuthenticationProtocol authProtocol)

Description copied from interface: PrivacyProtocol

Extend a localized key that is too short. Some privacy protocols require a key that is longer than the key generated by the password-to-key algorithm of the authentication protocol. This function extends a short key to the required length.

Specified by:

extendShortKey in interface PrivacyProtocol

Parameters:

shortKey - the short key that was generated using AuthenticationProtocol.passwordToKey(org.snmp4j.smi.OctetString, byte[]) function.

password - the password to use for key extension.

engineID - the SNMP engine ID of the authoritative engine.

authProtocol - the authentication protocol that should be used.

Returns:

the extended key or shortKey if no extension is needed.