com.microej.crypto.internal.cipher

Class AbstractRSACipherSpi

java.lang.Object

javax.crypto.CipherSpi

com.microej.crypto.internal.cipher.AbstractRSACipherSpi

Direct Known Subclasses:

NativeRSACipherSpi

public abstract class AbstractRSACipherSpi
extends CipherSpi

RSA cipher implementation. Supports RSA en/decryption and signing/verifying using both PKCS#1 v1.5 and OAEP (v2.2) paddings and without padding (raw RSA). Note that raw RSA is supported mostly for completeness and should only be used in rare cases. Objects should be instantiated by calling Cipher.getInstance() using the following algorithm names: . "RSA/ECB/PKCS1Padding" (or "RSA") for PKCS#1 v1.5 padding. . "RSA/ECB/OAEPwithhashandMGF1Padding" (or "RSA/ECB/OAEPPadding") for PKCS#1 v2.2 padding. . "RSA/ECB/NoPadding" for rsa RSA. We only do one RSA operation per doFinal() call. If the application passes more data via calls to update() or doFinal(), we throw an IllegalBlockSizeException when doFinal() is called (see JCE API spec). Bulk encryption using RSA does not make sense and is not standardized. Note: RSA keys should be at least 512 bits long

Since:

1.5

Author:

Andreas Sterbenz

Constructor Summary

Constructors

Constructor and Description
AbstractRSACipherSpi() Default constructor.
AbstractRSACipherSpi(int paddingType, int oaepHashAlgorithm) Custom constructor.

Method Summary

Modifier and Type	Method and Description
protected abstract int	decrypt(byte[] in, int inOffset, int inLength, byte[] output, int outputOffset) Decrypt a buffer with the RSA cipher.
protected abstract int	encrypt(byte[] in, int inOffset, int inLength, byte[] output, int outputOffset) Encrypt a buffer with the RSA cipher.
protected byte[]	engineDoFinal(byte[] in, int inOfs, int inLen) Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
protected int	engineDoFinal(byte[] in, int inOfs, int inLen, byte[] out, int outOfs) Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
protected int	engineGetBlockSize() Returns the block size (in bytes).
protected byte[]	engineGetIV() Returns the initialization vector (IV) in a new buffer.
protected int	engineGetOutputSize(int inputLen) Returns the length in bytes that an output buffer would need to be in order to hold the result of the next update or doFinal operation, given the input length inputLen (in bytes).
protected void	engineInit(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random) Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.
protected void	engineInit(int opmode, Key key, SecureRandom random) Initializes this cipher with a key and a source of randomness.
protected byte[]	engineUpdate(byte[] in, int inOfs, int inLen) Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
protected int	engineUpdate(byte[] in, int inOfs, int inLen, byte[] out, int outOfs) Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.
protected abstract void	init(NativePublicKey publicKey, NativePrivateKey privateKey, int padding, int hash) Initialize the native part of the RSA cipher.

Methods inherited from class javax.crypto.CipherSpi

engineUnwrap, engineUpdateAAD, engineWrap

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractRSACipherSpi

public AbstractRSACipherSpi()

Default constructor.

AbstractRSACipherSpi

public AbstractRSACipherSpi(int paddingType,
                            int oaepHashAlgorithm)

Custom constructor.

Parameters:

paddingType - one of PAD_* above.

oaepHashAlgorithm - one of OAEP_HASH_* above.

Method Detail

decrypt

protected abstract int decrypt(byte[] in,
                               int inOffset,
                               int inLength,
                               byte[] output,
                               int outputOffset)

Decrypt a buffer with the RSA cipher.

Parameters:

in - input buffer

inOffset - offset in the input buffer

inLength - input buffer length

output - output buffer

outputOffset - offset in the output buffer length

Returns:

the size of the decrypted data

encrypt

protected abstract int encrypt(byte[] in,
                               int inOffset,
                               int inLength,
                               byte[] output,
                               int outputOffset)

Encrypt a buffer with the RSA cipher.

Parameters:

in - input buffer

inOffset - offset in the input buffer

inLength - input buffer length

output - output buffer

outputOffset - offset in the output buffer length

Returns:

the size of the encrypted data

engineDoFinal

protected byte[] engineDoFinal(byte[] in,
                               int inOfs,
                               int inLen)
                        throws BadPaddingException,
                               IllegalBlockSizeException

Description copied from class: CipherSpi

Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.

The first inputLen bytes in the input buffer, starting at inputOffset inclusive, and any input bytes that may have been buffered during a previous update operation, are processed, with padding (if requested) being applied. If an AEAD mode such as GCM/CCM is being used, the authentication tag is appended in the case of encryption, or verified in the case of decryption. The result is stored in a new buffer.

Upon finishing, this method resets this cipher object to the state it was in when previously initialized via a call to engineInit. That is, the object is reset and available to encrypt or decrypt (depending on the operation mode that was specified in the call to engineInit) more data.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Specified by:

engineDoFinal in class CipherSpi

Parameters:

in - the input buffer

inOfs - the offset in input where the input starts

inLen - the input length

Returns:

the new buffer with the result

Throws:

BadPaddingException - if this cipher is in decryption mode, and (un)padding has been requested, but the decrypted data is not bounded by the appropriate padding bytes

AEADBadTagException - if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value

IllegalBlockSizeException - if this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data processed by this cipher is not a multiple of block size; or if this encryption algorithm is unable to process the input data provided.

engineDoFinal

protected int engineDoFinal(byte[] in,
                            int inOfs,
                            int inLen,
                            byte[] out,
                            int outOfs)
                     throws ShortBufferException,
                            BadPaddingException,
                            IllegalBlockSizeException

Description copied from class: CipherSpi

Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.

The first inputLen bytes in the input buffer, starting at inputOffset inclusive, and any input bytes that may have been buffered during a previous update operation, are processed, with padding (if requested) being applied. If an AEAD mode such as GCM/CCM is being used, the authentication tag is appended in the case of encryption, or verified in the case of decryption. The result is stored in the output buffer, starting at outputOffset inclusive.

If the output buffer is too small to hold the result, a ShortBufferException is thrown.

Upon finishing, this method resets this cipher object to the state it was in when previously initialized via a call to engineInit. That is, the object is reset and available to encrypt or decrypt (depending on the operation mode that was specified in the call to engineInit) more data.

Note: if any exception is thrown, this cipher object may need to be reset before it can be used again.

Specified by:

engineDoFinal in class CipherSpi

Parameters:

in - the input buffer

inOfs - the offset in input where the input starts

inLen - the input length

out - the buffer for the result

outOfs - the offset in output where the result is stored

Returns:

the number of bytes stored in output

Throws:

ShortBufferException - if the given output buffer is too small to hold the result

BadPaddingException - if this cipher is in decryption mode, and (un)padding has been requested, but the decrypted data is not bounded by the appropriate padding bytes

AEADBadTagException - if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value

IllegalBlockSizeException - if this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data processed by this cipher is not a multiple of block size; or if this encryption algorithm is unable to process the input data provided.

engineGetBlockSize

protected int engineGetBlockSize()

Description copied from class: CipherSpi

Returns the block size (in bytes).

Specified by:

engineGetBlockSize in class CipherSpi

Returns:

the block size (in bytes), or 0 if the underlying algorithm is not a block cipher

engineGetIV

protected byte[] engineGetIV()

Description copied from class: CipherSpi

Returns the initialization vector (IV) in a new buffer.

This is useful in the context of password-based encryption or decryption, where the IV is derived from a user-provided passphrase.

Specified by:

engineGetIV in class CipherSpi

Returns:

the initialization vector in a new buffer, or null if the underlying algorithm does not use an IV, or if the IV has not yet been set.

engineGetOutputSize

protected int engineGetOutputSize(int inputLen)

Description copied from class: CipherSpi

Returns the length in bytes that an output buffer would need to be in order to hold the result of the next update or doFinal operation, given the input length inputLen (in bytes).

This call takes into account any unprocessed (buffered) data from a previous update call, padding, and AEAD tagging.

The actual output length of the next update or doFinal call may be smaller than the length returned by this method.

Specified by:

engineGetOutputSize in class CipherSpi

Parameters:

inputLen - the input length (in bytes)

Returns:

the required output buffer size (in bytes)

engineInit

protected void engineInit(int opmode,
                          Key key,
                          AlgorithmParameterSpec params,
                          SecureRandom random)
                   throws InvalidKeyException,
                          InvalidAlgorithmParameterException

Description copied from class: CipherSpi

Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness.

The cipher is initialized for one of the following four operations: encryption, decryption, key wrapping or key unwrapping, depending on the value of opmode.

If this cipher requires any algorithm parameters and params is null, the underlying cipher implementation is supposed to generate the required parameters itself (using provider-specific default or random values) if it is being initialized for encryption or key wrapping, and raise an InvalidAlgorithmParameterException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using engineGetParameters or engineGetIV (if the parameter is an IV).

If this cipher requires algorithm parameters that cannot be derived from the input parameters, and there are no reasonable provider-specific default values, initialization will necessarily fail.

If this cipher (including its underlying feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them from random.

Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher and initializing it.

Specified by:

engineInit in class CipherSpi

Parameters:

opmode - the operation mode of this cipher (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)

key - the encryption key

params - the algorithm parameters

random - the source of randomness

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher

InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher, or if this cipher requires algorithm parameters and params is null.

engineInit

protected void engineInit(int opmode,
                          Key key,
                          SecureRandom random)
                   throws InvalidKeyException

Description copied from class: CipherSpi

Initializes this cipher with a key and a source of randomness.

The cipher is initialized for one of the following four operations: encryption, decryption, key wrapping or key unwrapping, depending on the value of opmode.

If this cipher requires any algorithm parameters that cannot be derived from the given key, the underlying cipher implementation is supposed to generate the required parameters itself (using provider-specific default or random values) if it is being initialized for encryption or key wrapping, and raise an InvalidKeyException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using engineGetParameters or engineGetIV (if the parameter is an IV).

If this cipher requires algorithm parameters that cannot be derived from the input parameters, and there are no reasonable provider-specific default values, initialization will necessarily fail.

If this cipher (including its underlying feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them from random.

Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher and initializing it.

Specified by:

engineInit in class CipherSpi

Parameters:

opmode - the operation mode of this cipher (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)

key - the encryption key

random - the source of randomness

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher, or requires algorithm parameters that cannot be determined from the given key.

engineUpdate

protected byte[] engineUpdate(byte[] in,
                              int inOfs,
                              int inLen)

Description copied from class: CipherSpi

Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.

The first inputLen bytes in the input buffer, starting at inputOffset inclusive, are processed, and the result is stored in a new buffer.

Specified by:

engineUpdate in class CipherSpi

Parameters:

in - the input buffer

inOfs - the offset in input where the input starts

inLen - the input length

Returns:

the new buffer with the result, or null if the underlying cipher is a block cipher and the input data is too short to result in a new block.

engineUpdate

protected int engineUpdate(byte[] in,
                           int inOfs,
                           int inLen,
                           byte[] out,
                           int outOfs)

Description copied from class: CipherSpi

Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part.

The first inputLen bytes in the input buffer, starting at inputOffset inclusive, are processed, and the result is stored in the output buffer, starting at outputOffset inclusive.

If the output buffer is too small to hold the result, a ShortBufferException is thrown.

Specified by:

engineUpdate in class CipherSpi

Parameters:

in - the input buffer

inOfs - the offset in input where the input starts

inLen - the input length

out - the buffer for the result

outOfs - the offset in output where the result is stored

Returns:

the number of bytes stored in output

init

protected abstract void init(NativePublicKey publicKey,
                             NativePrivateKey privateKey,
                             int padding,
                             int hash)

Initialize the native part of the RSA cipher.

Parameters:

publicKey - Public key of the RSA cipher (null for decryption).

privateKey - Private key of the RSA cipher (null for encryption).

padding - Padding scheme of the RSA cipher.

hash - Hash algorithm of the RSA cipher (valid only for OAEP with MGF1 padding scheme).