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/**
* Copyright (C) 2011 Ovea
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.ovea.tadjin.util.crypto;
import java.io.InputStream;
import java.io.OutputStream;
/**
* A {@code CipherService} uses a cryptographic algorithm called a
* Cipher to convert an original input source using a {@code key} to
* an uninterpretable format. The resulting encrypted output is only able to be converted back to original form with
* a {@code key} as well. {@code CipherService}s can perform both encryption and decryption.
* Cipher Basics
* For what is known as Symmetric {@code Cipher}s, the {@code Key} used to encrypt the source is the same
* as (or trivially similar to) the {@code Key} used to decrypt it.
*
* For Asymmetric {@code Cipher}s, the encryption {@code Key} is not the same as the decryption {@code Key}.
* The most common type of Asymmetric Ciphers are based on what is called public/private key pairs:
*
* A private key is known only to a single party, and as its name implies, is supposed be kept very private
* and secure. A public key that is associated with the private key can be disseminated freely to anyone.
* Then data encrypted by the public key can only be decrypted by the private key and vice versa, but neither party
* need share their private key with anyone else. By not sharing a private key, you can guarantee no 3rd party can
* intercept the key and therefore use it to decrypt a message.
*
* This asymmetric key technology was created as a
* more secure alternative to symmetric ciphers that sometimes suffer from man-in-the-middle attacks since, for
* data shared between two parties, the same Key must also be shared and may be compromised.
*
* Note that a symmetric cipher is perfectly fine to use if you just want to encode data in a format no one else
* can understand and you never give away the key. Shiro uses a symmetric cipher when creating certain
* HTTP Cookies for example - because it is often undesirable to have user's identity stored in a plain-text cookie,
* that identity can be converted via a symmetric cipher. Since the the same exact Shiro application will receive
* the cookie, it can decrypt it via the same {@code Key} and there is no potential for discovery since that Key
* is never shared with anyone.
* {@code CipherService}s vs JDK {@link javax.crypto.Cipher Cipher}s
* Shiro {@code CipherService}s essentially do the same things as JDK {@link javax.crypto.Cipher Cipher}s, but in
* simpler and easier-to-use ways for most application developers. When thinking about encrypting and decrypting data
* in an application, most app developers want what a {@code CipherService} provides, rather than having to manage the
* lower-level intricacies of the JDK's {@code Cipher} API. Here are a few reasons why most people prefer
* {@code CipherService}s:
*
* - Stateless Methods - {@code CipherService} method calls do not retain state between method invocations.
* JDK {@code Cipher} instances do retain state across invocations, requiring its end-users to manage the instance
* and its state themselves.
* - Thread Safety - {@code CipherService} instances are thread-safe inherently because no state is
* retained across method invocations. JDK {@code Cipher} instances retain state and cannot be used by multiple
* threads concurrently.
* - Single Operation - {@code CipherService} method calls are single operation methods: encryption or
* decryption in their entirety are done as a single method call. This is ideal for the large majority of developer
* needs where you have something unencrypted and just want it decrypted (or vice versa) in a single method call. In
* contrast, JDK {@code Cipher} instances can support encrypting/decrypting data in chunks over time (because it
* retains state), but this often introduces API clutter and confusion for most application developers.
* - Type Safe - There are {@code CipherService} implementations for different Cipher algorithms
* ({@code AesCipherService}, {@code BlowfishCipherService}, etc). There is only one JDK {@code Cipher} class to
* represent all cipher algorithms/instances.
*
- Simple Construction - Because {@code CipherService} instances are type-safe, instantiating and using
* one is often as simple as calling the default constructor, for example,
new AesCipherService();. The
* JDK {@code Cipher} class however requires using a procedural factory method with String arguments to indicate how
* the instance should be created. The String arguments themselves are somewhat cryptic and hard to
* understand unless you're a security expert. Shiro hides these details from you, but allows you to configure them
* if you want.
*
*/
public interface CipherService {
/**
* Decrypts encrypted data via the specified cipher key and returns the original (pre-encrypted) data.
* Note that the key must be in a format understood by the CipherService implementation.
*
* @param encrypted the previously encrypted data to decrypt
* @param decryptionKey the cipher key used during decryption.
* @return a byte source representing the original form of the specified encrypted data.
* @throws CryptoException if there is an error during decryption
*/
byte[] decrypt(byte[] encrypted, byte[] decryptionKey) throws CryptoException;
/**
* Receives encrypted data from the given {@code InputStream}, decrypts it, and sends the resulting decrypted data
* to the given {@code OutputStream}.
*
* NOTE: This method does NOT flush or close either stream prior to returning - the caller must
* do so when they are finished with the streams. For example:
*
* try {
* InputStream in = ...
* OutputStream out = ...
* cipherService.decrypt(in, out, decryptionKey);
* } finally {
* if (in != null) {
* try {
* in.close();
* } catch (IOException ioe1) { ... log, trigger event, etc }
* }
* if (out != null) {
* try {
* out.close();
* } catch (IOException ioe2) { ... log, trigger event, etc }
* }
* }
*
*
* @param in the stream supplying the data to decrypt
* @param out the stream to send the decrypted data
* @param decryptionKey the cipher key to use for decryption
* @throws CryptoException if there is any problem during decryption.
*/
void decrypt(InputStream in, OutputStream out, byte[] decryptionKey) throws CryptoException;
/**
* Encrypts data via the specified cipher key. Note that the key must be in a format understood by
* the {@code CipherService} implementation.
*
* @param raw the data to encrypt
* @param encryptionKey the cipher key used during encryption.
* @return a byte source with the encrypted representation of the specified raw data.
* @throws CryptoException if there is an error during encryption
*/
byte[] encrypt(byte[] raw, byte[] encryptionKey) throws CryptoException;
/**
* Receives the data from the given {@code InputStream}, encrypts it, and sends the resulting encrypted data to the
* given {@code OutputStream}.
*
* NOTE: This method does NOT flush or close either stream prior to returning - the caller must
* do so when they are finished with the streams. For example:
*
* try {
* InputStream in = ...
* OutputStream out = ...
* cipherService.encrypt(in, out, encryptionKey);
* } finally {
* if (in != null) {
* try {
* in.close();
* } catch (IOException ioe1) { ... log, trigger event, etc }
* }
* if (out != null) {
* try {
* out.close();
* } catch (IOException ioe2) { ... log, trigger event, etc }
* }
* }
*
*
* @param in the stream supplying the data to encrypt
* @param out the stream to send the encrypted data
* @param encryptionKey the cipher key to use for encryption
* @throws CryptoException if there is any problem during encryption.
*/
void encrypt(InputStream in, OutputStream out, byte[] encryptionKey) throws CryptoException;
}