# Poco::Crypto

# class Cipher

Library: Crypto
Package: Cipher
Header: Poco/Crypto/Cipher.h

## Description

Represents the abstract base class from which all implementations of symmetric/assymetric encryption algorithms must inherit. Use the CipherFactory class to obtain an instance of this class:

    CipherFactory& factory = CipherFactory::defaultFactory();
    // Creates a 256-bit AES cipher
    Cipher* pCipher = factory.createCipher(CipherKey("aes-256"));
    Cipher* pRSACipher = factory.createCipher(RSAKey(RSAKey::KL_1024, RSAKey::EXP_SMALL));

Check the different Key constructors on how to initialize/create a key. The above example auto-generates random keys.

Note that you won't be able to decrypt data encrypted with a random key once the Cipher is destroyed unless you persist the generated key and IV. An example usage for random keys is to encrypt data saved in a temporary file.

Once your key is set up, you can use the Cipher object to encrypt or decrypt strings or, in conjunction with a CryptoInputStream or a CryptoOutputStream, to encrypt streams of data.

Since encrypted strings will contain arbitary binary data that will cause problems in applications that are not binary-safe (eg., when sending encrypted data in e-mails), the encryptString() and decryptString() can encode (or decode, respectively) encrypted data using a "transport encoding". Supported encodings are Base64 and BinHex.

The following example encrypts and decrypts a string utilizing Base64 encoding:

    std::string plainText = "This is my secret information";
    std::string encrypted = pCipher->encryptString(plainText, Cipher::ENC_BASE64);
    std::string decrypted = pCipher->decryptString(encrypted, Cipher::ENC_BASE64);

In order to encrypt a stream of data (eg. to encrypt files), you can use a CryptoStream:

    // Create an output stream that will encrypt all data going through it
    // and write pass it to the underlying file stream.
    Poco::FileOutputStream sink("encrypted.dat");
    CryptoOutputStream encryptor(sink, pCipher->createEncryptor());

    Poco::FileInputStream source("source.txt");
    Poco::StreamCopier::copyStream(source, encryptor);

    // Always close output streams to flush all internal buffers
    encryptor.close();
    sink.close();

## Inheritance

Direct Base Classes: Poco::RefCountedObject

All Base Classes: Poco::RefCountedObject

Known Derived Classes: CipherImpl, RSACipherImpl

## Member Summary

Member Functions: createDecryptor, createEncryptor, decrypt, decryptString, encrypt, encryptString, name

Inherited Functions: duplicate, referenceCount, release

## Types

### ByteVec

typedef std::vector < unsigned char > ByteVec;

### Ptr

typedef Poco::AutoPtr < Cipher > Ptr;

## Enumerations

### Encoding

Transport encoding to use for encryptString() and decryptString().

ENC_NONE

Plain binary output

ENC_BASE64

Base64-encoded output

ENC_BINHEX

BinHex-encoded output

## Constructors

### Cipher

Cipher();

Creates a new Cipher object.

## Destructor

### ~Cipher

virtual ~Cipher();

Destroys the Cipher.

## Member Functions

### createDecryptor

virtual CryptoTransform * createDecryptor() = 0;

Creates a decryptor object to be used with a CryptoStream.

### createEncryptor

virtual CryptoTransform * createEncryptor() = 0;

Creates an encrytor object to be used with a CryptoStream.

### decrypt

virtual void decrypt(
std::istream & source,
std::ostream & sink,
Encoding encoding = ENC_NONE
);

Directly decrypt an input stream that is encoded with the given encoding.

### decryptString

virtual std::string decryptString(
const std::string & str,
Encoding encoding = ENC_NONE
);

Directly decrypt a string that is encoded with the given encoding.

### encrypt

virtual void encrypt(
std::istream & source,
std::ostream & sink,
Encoding encoding = ENC_NONE
);

Directly encrypts an input stream and encodes it using the given encoding.

### encryptString

virtual std::string encryptString(
const std::string & str,
Encoding encoding = ENC_NONE
);

Directly encrypt a string and encode it using the given encoding.

### name

virtual const std::string & name() const = 0;

Returns the name of the Cipher.