Key factories are used to convert keys (opaque
* cryptographic keys of type Key) into key specifications
* (transparent representations of the underlying key material), and vice
* versa.
* Secret key factories operate only on secret (symmetric) keys.
*
*
Key factories are bi-directional, i.e., they allow to build an opaque * key object from a given key specification (key material), or to retrieve * the underlying key material of a key object in a suitable format. * *
Application developers should refer to their provider's documentation
* to find out which key specifications are supported by the
* {@link #generateSecret(java.security.spec.KeySpec) generateSecret} and
* {@link #getKeySpec(javax.crypto.SecretKey, java.lang.Class) getKeySpec}
* methods.
* For example, the DES secret-key factory supplied by the "SunJCE" provider
* supports DESKeySpec as a transparent representation of DES
* keys, and that provider's secret-key factory for Triple DES keys supports
* DESedeKeySpec as a transparent representation of Triple DES
* keys.
*
*
Android provides the following SecretKeyFactory algorithms:
*
| Algorithm | *Supported API Levels | *
|---|---|
| AES | *23+ | *
| DES | *1+ | *
| DESede | *1+ | *
| HmacSHA1 | *23+ | *
| HmacSHA224 | *23+ | *
| HmacSHA256 | *23+ | *
| HmacSHA384 | *23+ | *
| HmacSHA512 | *23+ | *
| PBEwithHmacSHA1 | *1+ | *
| PBEwithHmacSHA1AndAES_128 | *26+ | *
| PBEwithHmacSHA1AndAES_256 | *26+ | *
| PBEwithHmacSHA224AndAES_128 | *26+ | *
| PBEwithHmacSHA224AndAES_256 | *26+ | *
| PBEwithHmacSHA256AndAES_128 | *26+ | *
| PBEwithHmacSHA256AndAES_256 | *26+ | *
| PBEwithHmacSHA384AndAES_128 | *26+ | *
| PBEwithHmacSHA384AndAES_256 | *26+ | *
| PBEwithHmacSHA512AndAES_128 | *26+ | *
| PBEwithHmacSHA512AndAES_256 | *26+ | *
| PBEwithMD5AND128BITAES-CBC-OPENSSL | *1+ | *
| PBEwithMD5AND192BITAES-CBC-OPENSSL | *1+ | *
| PBEwithMD5AND256BITAES-CBC-OPENSSL | *1+ | *
| PBEwithMD5ANDDES | *1+ | *
| PBEwithMD5ANDRC2 | *1+ | *
| PBEwithSHA1ANDDES | *1+ | *
| PBEwithSHA1ANDRC2 | *1+ | *
| PBEwithSHA256AND128BITAES-CBC-BC | *1+ | *
| PBEwithSHA256AND192BITAES-CBC-BC | *1+ | *
| PBEwithSHA256AND256BITAES-CBC-BC | *1+ | *
| PBEwithSHAAND128BITAES-CBC-BC | *1+ | *
| PBEwithSHAAND128BITRC2-CBC | *10+ | *
| PBEwithSHAAND128BITRC4 | *10+ | *
| PBEwithSHAAND192BITAES-CBC-BC | *1+ | *
| PBEwithSHAAND2-KEYTRIPLEDES-CBC | *1+ | *
| PBEwithSHAAND256BITAES-CBC-BC | *1+ | *
| PBEwithSHAAND3-KEYTRIPLEDES-CBC | *1+ | *
| PBEwithSHAAND40BITRC2-CBC | *1+ | *
| PBEwithSHAAND40BITRC4 | *10+ | *
| PBEwithSHAANDTWOFISH-CBC | *10+ | *
| PBKDF2withHmacSHA1 | *10+ | *
| PBKDF2withHmacSHA1And8BIT | *19+ | *
| PBKDF2withHmacSHA224 | *26+ | *
| PBKDF2withHmacSHA256 | *26+ | *
| PBKDF2withHmacSHA384 | *26+ | *
| PBKDF2withHmacSHA512 | *26+ | *
SecretKeyFactory object that converts
* secret keys of the specified algorithm.
*
* This method traverses the list of registered security Providers, * starting with the most preferred Provider. * A new SecretKeyFactory object encapsulating the * SecretKeyFactorySpi implementation from the first * Provider that supports the specified algorithm is returned. * *
Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the standard name of the requested secret-key
* algorithm.
* See the SecretKeyFactory section in the
* Java Cryptography Architecture Standard Algorithm Name Documentation
* for information about standard algorithm names.
*
* @return the new SecretKeyFactory object.
*
* @exception NullPointerException if the specified algorithm
* is null.
*
* @exception NoSuchAlgorithmException if no Provider supports a
* SecretKeyFactorySpi implementation for the
* specified algorithm.
*
* @see java.security.Provider
*/
public static final SecretKeyFactory getInstance(String algorithm)
throws NoSuchAlgorithmException {
return new SecretKeyFactory(algorithm);
}
/**
* Returns a SecretKeyFactory object that converts
* secret keys of the specified algorithm.
*
*
A new SecretKeyFactory object encapsulating the * SecretKeyFactorySpi implementation from the specified provider * is returned. The specified provider must be registered * in the security provider list. * *
Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the standard name of the requested secret-key
* algorithm.
* See the SecretKeyFactory section in the
* Java Cryptography Architecture Standard Algorithm Name Documentation
* for information about standard algorithm names.
*
* @param provider the name of the provider.
*
* @return the new SecretKeyFactory object.
*
* @exception NoSuchAlgorithmException if a SecretKeyFactorySpi
* implementation for the specified algorithm is not
* available from the specified provider.
*
* @exception NullPointerException if the specified algorithm
* is null.
*
* @throws NoSuchProviderException if the specified provider is not
* registered in the security provider list.
*
* @exception IllegalArgumentException if the provider
* is null or empty.
*
* @see java.security.Provider
*/
public static final SecretKeyFactory getInstance(String algorithm,
String provider) throws NoSuchAlgorithmException,
NoSuchProviderException {
Instance instance = JceSecurity.getInstance("SecretKeyFactory",
SecretKeyFactorySpi.class, algorithm, provider);
return new SecretKeyFactory((SecretKeyFactorySpi)instance.impl,
instance.provider, algorithm);
}
/**
* Returns a SecretKeyFactory object that converts
* secret keys of the specified algorithm.
*
*
A new SecretKeyFactory object encapsulating the
* SecretKeyFactorySpi implementation from the specified Provider
* object is returned. Note that the specified Provider object
* does not have to be registered in the provider list.
*
* @param algorithm the standard name of the requested secret-key
* algorithm.
* See the SecretKeyFactory section in the
* Java Cryptography Architecture Standard Algorithm Name Documentation
* for information about standard algorithm names.
*
* @param provider the provider.
*
* @return the new SecretKeyFactory object.
*
* @exception NullPointerException if the specified algorithm
* is null.
*
* @exception NoSuchAlgorithmException if a SecretKeyFactorySpi
* implementation for the specified algorithm is not available
* from the specified Provider object.
*
* @exception IllegalArgumentException if the provider
* is null.
*
* @see java.security.Provider
*/
public static final SecretKeyFactory getInstance(String algorithm,
Provider provider) throws NoSuchAlgorithmException {
Instance instance = JceSecurity.getInstance("SecretKeyFactory",
SecretKeyFactorySpi.class, algorithm, provider);
return new SecretKeyFactory((SecretKeyFactorySpi)instance.impl,
instance.provider, algorithm);
}
/**
* Returns the provider of this SecretKeyFactory object.
*
* @return the provider of this SecretKeyFactory object
*/
public final Provider getProvider() {
synchronized (lock) {
// disable further failover after this call
serviceIterator = null;
return provider;
}
}
/**
* Returns the algorithm name of this SecretKeyFactory object.
*
*
This is the same name that was specified in one of the
* getInstance calls that created this
* SecretKeyFactory object.
*
* @return the algorithm name of this SecretKeyFactory
* object.
*/
public final String getAlgorithm() {
return this.algorithm;
}
/**
* Update the active spi of this class and return the next
* implementation for failover. If no more implemenations are
* available, this method returns null. However, the active spi of
* this class is never set to null.
*/
private SecretKeyFactorySpi nextSpi(SecretKeyFactorySpi oldSpi) {
synchronized (lock) {
// somebody else did a failover concurrently
// try that spi now
if ((oldSpi != null) && (oldSpi != spi)) {
return spi;
}
if (serviceIterator == null) {
return null;
}
while (serviceIterator.hasNext()) {
Service s = serviceIterator.next();
if (JceSecurity.canUseProvider(s.getProvider()) == false) {
continue;
}
try {
Object obj = s.newInstance(null);
if (obj instanceof SecretKeyFactorySpi == false) {
continue;
}
SecretKeyFactorySpi spi = (SecretKeyFactorySpi)obj;
provider = s.getProvider();
this.spi = spi;
return spi;
} catch (NoSuchAlgorithmException e) {
// ignore
}
}
serviceIterator = null;
return null;
}
}
/**
* Generates a SecretKey object from the provided key
* specification (key material).
*
* @param keySpec the specification (key material) of the secret key
*
* @return the secret key
*
* @exception InvalidKeySpecException if the given key specification
* is inappropriate for this secret-key factory to produce a secret key.
*/
public final SecretKey generateSecret(KeySpec keySpec)
throws InvalidKeySpecException {
if (serviceIterator == null) {
return spi.engineGenerateSecret(keySpec);
}
Exception failure = null;
SecretKeyFactorySpi mySpi = spi;
do {
try {
return mySpi.engineGenerateSecret(keySpec);
} catch (Exception e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi);
}
} while (mySpi != null);
if (failure instanceof InvalidKeySpecException) {
throw (InvalidKeySpecException)failure;
}
throw new InvalidKeySpecException
("Could not generate secret key", failure);
}
/**
* Returns a specification (key material) of the given key object
* in the requested format.
*
* @param key the key
* @param keySpec the requested format in which the key material shall be
* returned
*
* @return the underlying key specification (key material) in the
* requested format
*
* @exception InvalidKeySpecException if the requested key specification is
* inappropriate for the given key (e.g., the algorithms associated with
* key and keySpec do not match, or
* key references a key on a cryptographic hardware device
* whereas keySpec is the specification of a software-based
* key), or the given key cannot be dealt with
* (e.g., the given key has an algorithm or format not supported by this
* secret-key factory).
*/
public final KeySpec getKeySpec(SecretKey key, Class keySpec)
throws InvalidKeySpecException {
if (serviceIterator == null) {
return spi.engineGetKeySpec(key, keySpec);
}
Exception failure = null;
SecretKeyFactorySpi mySpi = spi;
do {
try {
return mySpi.engineGetKeySpec(key, keySpec);
} catch (Exception e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi);
}
} while (mySpi != null);
if (failure instanceof InvalidKeySpecException) {
throw (InvalidKeySpecException)failure;
}
throw new InvalidKeySpecException
("Could not get key spec", failure);
}
/**
* Translates a key object, whose provider may be unknown or potentially
* untrusted, into a corresponding key object of this secret-key factory.
*
* @param key the key whose provider is unknown or untrusted
*
* @return the translated key
*
* @exception InvalidKeyException if the given key cannot be processed
* by this secret-key factory.
*/
public final SecretKey translateKey(SecretKey key)
throws InvalidKeyException {
if (serviceIterator == null) {
return spi.engineTranslateKey(key);
}
Exception failure = null;
SecretKeyFactorySpi mySpi = spi;
do {
try {
return mySpi.engineTranslateKey(key);
} catch (Exception e) {
if (failure == null) {
failure = e;
}
mySpi = nextSpi(mySpi);
}
} while (mySpi != null);
if (failure instanceof InvalidKeyException) {
throw (InvalidKeyException)failure;
}
throw new InvalidKeyException
("Could not translate key", failure);
}
}