SimpleCrypt Class Reference

Simple encryption and decryption of strings and byte arrays. More...

#include <SimpleCrypt.h>

Public Types
enum	CompressionMode { CompressionAuto , CompressionAlways , CompressionNever }
enum	IntegrityProtectionMode { ProtectionNone , ProtectionChecksum , ProtectionHash }
enum	Error { ErrorNoError , ErrorNoKeySet , ErrorUnknownVersion , ErrorIntegrityFailed }
enum	CryptoFlag { CryptoFlagNone = 0 , CryptoFlagCompression = 0x01 , CryptoFlagChecksum = 0x02 , CryptoFlagHash = 0x04 }

Public Member Functions
	SimpleCrypt ()
	Constructor. SimpleCrypt. More...
	SimpleCrypt (quint64 key)
	Constructor. SimpleCrypt. More...
void	setKey (quint64 key)
	set Key. setKey More...
bool	hasKey () const
void	setCompressionMode (CompressionMode mode)
CompressionMode	compressionMode () const
void	setIntegrityProtectionMode (IntegrityProtectionMode mode)
IntegrityProtectionMode	integrityProtectionMode () const
Error	lastError () const
QString	encryptToString (const QString &plaintext)
	encrypt To String QString. encryptToString More...
QString	encryptToString (const QByteArray &plaintext)
	encrypt To String QByteArray. encryptToString More...
QByteArray	encryptToByteArray (const QString &plaintext)
	encrypt To Byte Array QString. encryptToByteArray More...
QByteArray	encryptToByteArray (const QByteArray &plaintext)
	encrypt To Byte Array QByteArray. encryptToByteArray More...
QString	decryptToString (const QString &cyphertext)
	decrypt To String QString. decryptToString More...
QByteArray	decryptToByteArray (const QString &cyphertext)
	decrypt To Byte Array QString. decryptToByteArray More...
QString	decryptToString (const QByteArray &cypher)
	decrypt To String QByteArray. decryptToString More...
QByteArray	decryptToByteArray (QByteArray cypher)
	decrypt To Byte Array QByteArray. decryptToByteArray More...
	Q_DECLARE_FLAGS (CryptoFlags, CryptoFlag)
void	setDebugMessage (bool thisState)
	set Debug Message More...
bool	getDebugMessage ()
	get Debug Message More...
void	setMessage (const QString &thisMessage)
	set Message More...

Detailed Description

Simple encryption and decryption of strings and byte arrays.

This class provides a simple implementation of encryption and decryption of strings and byte arrays.

Warning

The encryption provided by this class is NOT strong encryption. It may help to shield things from curious eyes, but it will NOT stand up to someone determined to break the encryption. Do not say you were not warned.

The class uses a 64 bit key. Simply create an instance of the class, set the key, and use the encryptToString() method to calculate an encrypted version of the input string. To decrypt that string again, use an instance of SimpleCrypt initialized with the same key, and call the decryptToString() method with the encrypted string. If the key matches, the decrypted version of the string will be returned again.

If you do not provide a key, or if something else is wrong, the encryption and decryption function will return an empty string or will return a string containing nonsense. lastError() will return a value indicating if the method was succesful, and if not, why not.

SimpleCrypt is prepared for the case that the encryption and decryption algorithm is changed in a later version, by prepending a version identifier to the cypertext.

Definition at line 71 of file SimpleCrypt.h.

Member Enumeration Documentation

CompressionMode

enum SimpleCrypt::CompressionMode

CompressionMode describes if compression will be applied to the data to be encrypted.

Enumerator
CompressionAuto	Only apply compression if that results in a shorter plaintext.
CompressionAlways	Always apply compression. Note that for short inputs, a compression may result in longer data
CompressionNever	Never apply compression.

Definition at line 77 of file SimpleCrypt.h.

        {
            CompressionAuto,    
            CompressionAlways,  
            CompressionNever    
        };

CryptoFlag

enum SimpleCrypt::CryptoFlag

enum to describe options that have been used for the encryption. Currently only one, but that only leaves room for future extensions like adding a cryptographic hash...

Enumerator
CryptoFlagNone	CryptoFlagNone Crypto Flag None
CryptoFlagCompression	CryptoFlagCompression Crypto Flag Compression
CryptoFlagChecksum	CryptoFlagChecksum Crypto Flag Checksum
CryptoFlagHash	CryptoFlagHash Crypto Flag Hash

Definition at line 204 of file SimpleCrypt.h.

        {
            CryptoFlagNone        = 0,    
            CryptoFlagCompression = 0x01, 
            CryptoFlagChecksum    = 0x02, 
            CryptoFlagHash        = 0x04  
        };

Error

enum SimpleCrypt::Error

Enumerator
ErrorNoError	No error occurred.
ErrorNoKeySet	No key was set. You can not encrypt or decrypt without a valid key.
ErrorUnknownVersion	The version of this data is unknown, or the data is otherwise not valid.
ErrorIntegrityFailed	The integrity check of the data failed. Perhaps the wrong key was used.

Definition at line 96 of file SimpleCrypt.h.

        {
            ErrorNoError,         
            ErrorNoKeySet,        
            ErrorUnknownVersion,  
            ErrorIntegrityFailed  
        };

IntegrityProtectionMode

enum SimpleCrypt::IntegrityProtectionMode

IntegrityProtectionMode describes measures taken to make it possible to detect problems with the data, or wrong decryption keys. Measures involve adding a checksum or a cryptograhpic hash to the data to be encrypted. This increases the length of the resulting cypertext, but makes it possible to check if the plaintext appears to be valid after decryption.

Enumerator
ProtectionNone	The integerity of the encrypted data is not protected. It is not really possible to detect a wrong key, for instance.
ProtectionChecksum	A simple checksum is used to verify that the data is in order. If not, an empty string is returned.
ProtectionHash	A cryptographic hash is used to verify the integrity of the data. This method produces a much stronger, but longer check

Definition at line 89 of file SimpleCrypt.h.

        {
            ProtectionNone,    
            ProtectionChecksum,
            ProtectionHash     
        };

Constructor & Destructor Documentation

SimpleCrypt() [1/2]

SimpleCrypt::SimpleCrypt

(

)

Constructor. SimpleCrypt.

Constructor. Constructs a SimpleCrypt instance without a valid key set on it.

Definition at line 34 of file SimpleCrypt.cpp.

                        : myKey(0), myCompressionMode(CompressionAuto), myProtectionMode(ProtectionChecksum), myLastError(ErrorNoError)
{
    QRandomGenerator generator(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
    generator.generate();
    // qsrand(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
}

SimpleCrypt() [2/2]

SimpleCrypt::SimpleCrypt ( quint64  key )

explicit

Constructor. SimpleCrypt.

Constructor. Constructs a SimpleCrypt instance and initializes it with the given

• key.

Definition at line 44 of file SimpleCrypt.cpp.

                                   : myKey(key), myCompressionMode(CompressionAuto), myProtectionMode(ProtectionChecksum), myLastError(ErrorNoError)
{
    QRandomGenerator generator(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
    generator.generate();
    // qsrand(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
    splitKey();
}

Member Function Documentation

compressionMode()

CompressionMode SimpleCrypt::compressionMode ( ) const

inline

Returns the CompressionMode that is currently in use.

Definition at line 130 of file SimpleCrypt.h.

{return myCompressionMode;}

decryptToByteArray() [1/2]

QByteArray SimpleCrypt::decryptToByteArray

(

const QString &

cyphertext

)

decrypt To Byte Array QString. decryptToByteArray

Decrypts a cyphertext string encrypted with this class with the set key back to the plain text version.

If an error occured, such as non-matching keys between encryption and decryption, an empty string or a string containing nonsense may be returned.

Definition at line 222 of file SimpleCrypt.cpp.

{
    QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toLatin1());
    QByteArray ba = decryptToByteArray(cyphertextArray);
 
    return ba;
}

decryptToByteArray() [2/2]

QByteArray SimpleCrypt::decryptToByteArray

(

QByteArray

cypher

)

decrypt To Byte Array QByteArray. decryptToByteArray

Decrypts a cyphertext binary encrypted with this class with the set key back to the plain text version.

If an error occured, such as non-matching keys between encryption and decryption, an empty string or a string containing nonsense may be returned.

Definition at line 233 of file SimpleCrypt.cpp.

{
    if (myKeyParts.isEmpty())
    {
        qWarning() << "No key set.";
        myLastError = ErrorNoKeySet;
        return QByteArray();
    }
 
    QByteArray ba = cypher;
 
    if( cypher.count() < 3 )
        { return QByteArray(); }
 
    char version = ba.at(0);
 
    if (version != 3)
    {  // we only work with version 3
        myLastError = ErrorUnknownVersion;
        qWarning() << "Invalid version or not a cyphertext.";
        return QByteArray();
    }
 
    CryptoFlags flags = CryptoFlags(ba.at(1));
 
    ba = ba.mid(2);
    int pos(0);
    int cnt(ba.count());
    char lastChar = 0;
 
    while (pos < cnt)
    {
        char currentChar = ba[pos];
        ba[pos] = ba.at(pos) ^ lastChar ^ myKeyParts.at(pos % 8);
        lastChar = currentChar;
        ++pos;
    }
 
    ba = ba.mid(1); // chop off the random number at the start
 
    bool integrityOk(true);
    if (flags.testFlag(CryptoFlagChecksum))
    {
        if (ba.length() < 2)
        {
            myLastError = ErrorIntegrityFailed;
            return QByteArray();
        }
        quint16 storedChecksum;
        {
            QDataStream s(&ba, QIODevice::ReadOnly);
            s >> storedChecksum;
        }
        ba = ba.mid(2);
        quint16 checksum = qChecksum(ba.constData(), ba.length());
        integrityOk = (checksum == storedChecksum);
    }
    else if (flags.testFlag(CryptoFlagHash))
    {
        if (ba.length() < 20)
        {
            myLastError = ErrorIntegrityFailed;
            return QByteArray();
        }
        QByteArray storedHash = ba.left(20);
        ba = ba.mid(20);
        QCryptographicHash hash(QCryptographicHash::Sha1);
        hash.addData(ba);
        integrityOk = (hash.result() == storedHash);
    }
 
    if (!integrityOk)
    {
        myLastError = ErrorIntegrityFailed;
        return QByteArray();
    }
 
    if (flags.testFlag(CryptoFlagCompression))
       { ba = qUncompress(ba); }
 
    myLastError = ErrorNoError;
    return ba;
}

decryptToString() [1/2]

QString SimpleCrypt::decryptToString

(

const QByteArray &

cypher

)

decrypt To String QByteArray. decryptToString

Decrypts a cyphertext binary encrypted with this class with the set key back to the plain text version. If an error occured, such as non-matching keys between encryption and decryption, an empty string or a string containing nonsense may be returned.

Definition at line 211 of file SimpleCrypt.cpp.

{
    QByteArray ba = decryptToByteArray(cypher);
    QString plaintext = QString::fromUtf8(ba, ba.size());
 
    return plaintext;
}

decryptToString() [2/2]

QString SimpleCrypt::decryptToString

(

const QString &

cyphertext

)

decrypt To String QString. decryptToString

Decrypts a cyphertext string encrypted with this class with the set key back to the plain text version.

If an error occured, such as non-matching keys between encryption and decryption, an empty string or a string containing nonsense may be returned.

Definition at line 199 of file SimpleCrypt.cpp.

{
    QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toLatin1());
    QByteArray plaintextArray = decryptToByteArray(cyphertextArray);
    QString plaintext = QString::fromUtf8(plaintextArray, plaintextArray.size());
 
    return plaintext;
}

encryptToByteArray() [1/2]

QByteArray SimpleCrypt::encryptToByteArray

(

const QByteArray &

plaintext

)

encrypt To Byte Array QByteArray. encryptToByteArray

Encrypts the

• plaintext QByteArray with the key the class was initialized with, and returns a binary cyphertext in a QByteArray the result.

This method returns a byte array, that is useable for storing a binary format. If you need a string you can store in a text file, use encryptToString() instead.

Definition at line 105 of file SimpleCrypt.cpp.

{
    if (myKeyParts.isEmpty())
    {
        qWarning() << "No key set.";
        myLastError = ErrorNoKeySet;
        return QByteArray();
    }
 
    QByteArray ba = plaintext;
 
    CryptoFlags flags = CryptoFlagNone;
    if (myCompressionMode == CompressionAlways)
    {
        ba = qCompress(ba, 9); // maximum compression
        flags |= CryptoFlagCompression;
    }
    else if (myCompressionMode == CompressionAuto)
    {
        QByteArray compressed = qCompress(ba, 9);
        if (compressed.count() < ba.count())
        {
            ba = compressed;
            flags |= CryptoFlagCompression;
        }
    }
 
    QByteArray integrityProtection;
    if (myProtectionMode == ProtectionChecksum)
    {
        flags |= CryptoFlagChecksum;
        QDataStream s(&integrityProtection, QIODevice::WriteOnly);
        s << qChecksum(ba.constData(), ba.length());
    }
    else if (myProtectionMode == ProtectionHash)
    {
        flags |= CryptoFlagHash;
        QCryptographicHash hash(QCryptographicHash::Sha1);
        hash.addData(ba);
 
        integrityProtection += hash.result();
    }
    // prepend a random char to the string
    QRandomGenerator generator(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
    char randomChar = char(generator.generate() & 0xFF);
    // char randomChar = char(qrand() & 0xFF);
 
    ba = randomChar + integrityProtection + ba;
 
    int pos(0);
    char lastChar(0);
 
    int cnt = ba.count();
 
    while (pos < cnt)
    {
        ba[pos] = ba.at(pos) ^ myKeyParts.at(pos % 8) ^ lastChar;
        lastChar = ba.at(pos);
        ++pos;
    }
 
    QByteArray resultArray;
    resultArray.append(char(0x03));  // version for future updates to algorithm
    resultArray.append(char(flags)); // encryption flags
    resultArray.append(ba);
 
    myLastError = ErrorNoError;
    return resultArray;
}

encryptToByteArray() [2/2]

QByteArray SimpleCrypt::encryptToByteArray

(

const QString &

plaintext

)

encrypt To Byte Array QString. encryptToByteArray

Encrypts the

• plaintext string with the key the class was initialized with, and returns a binary cyphertext in a QByteArray the result.

This method returns a byte array, that is useable for storing a binary format. If you need a string you can store in a text file, use encryptToString() instead.

Definition at line 96 of file SimpleCrypt.cpp.

{
    QByteArray plaintextArray = plaintext.toUtf8();
    return encryptToByteArray(plaintextArray);
}

encryptToString() [1/2]

QString SimpleCrypt::encryptToString

(

const QByteArray &

plaintext

)

encrypt To String QByteArray. encryptToString

Encrypts the

• plaintext QByteArray with the key the class was initialized with, and returns a cyphertext the result. The result is a base64 encoded version of the binary array that is the actual result of the encryption, so it can be stored easily in a text format.

Definition at line 189 of file SimpleCrypt.cpp.

{
    QByteArray cypher = encryptToByteArray(plaintext);
    QString cypherString = QString::fromLatin1(cypher.toBase64());
    return cypherString;
}

encryptToString() [2/2]

QString SimpleCrypt::encryptToString

(

const QString &

plaintext

)

encrypt To String QString. encryptToString

Encrypts the

• plaintext string with the key the class was initialized with, and returns a cyphertext the result. The result is a base64 encoded version of the binary array that is the actual result of the string, so it can be stored easily in a text format.

Definition at line 178 of file SimpleCrypt.cpp.

{
    QByteArray plaintextArray = plaintext.toUtf8();
    QByteArray cypher = encryptToByteArray(plaintextArray);
    QString cypherString = QString::fromLatin1(cypher.toBase64());
    return cypherString;
}

getDebugMessage()

bool SimpleCrypt::getDebugMessage

(

)

get Debug Message

get Debug Message. getDebugMessage

Definition at line 63 of file SimpleCrypt.cpp.

{
    return isDebugMessage;
}

hasKey()

bool SimpleCrypt::hasKey ( ) const

inline

Returns true if SimpleCrypt has been initialized with a key.

Definition at line 120 of file SimpleCrypt.h.

{return !myKeyParts.isEmpty();}

integrityProtectionMode()

IntegrityProtectionMode SimpleCrypt::integrityProtectionMode ( ) const

inline

Definition at line 138 of file SimpleCrypt.h.

{return myProtectionMode;}

lastError()

Error SimpleCrypt::lastError ( ) const

inline

Definition at line 141 of file SimpleCrypt.h.

{return myLastError;}

Q_DECLARE_FLAGS()

SimpleCrypt::Q_DECLARE_FLAGS	(	CryptoFlags	,
		CryptoFlag
	)

setCompressionMode()

void SimpleCrypt::setCompressionMode ( CompressionMode  mode )

inline

Sets the compression mode to use when encrypting data. The default mode is Auto.

Note that decryption is not influenced by this mode, as the decryption recognizes what mode was used when encrypting.

Definition at line 126 of file SimpleCrypt.h.

{myCompressionMode = mode;}

setDebugMessage()

void SimpleCrypt::setDebugMessage

(

bool

thisState

)

set Debug Message

set Debug Message. setDebugMessage

Definition at line 55 of file SimpleCrypt.cpp.

{
    isDebugMessage = thisState;
}

setIntegrityProtectionMode()

void SimpleCrypt::setIntegrityProtectionMode ( IntegrityProtectionMode  mode )

inline

Sets the integrity mode to use when encrypting data. The default mode is Checksum.

Note that decryption is not influenced by this mode, as the decryption recognizes what mode was used when encrypting.

Definition at line 136 of file SimpleCrypt.h.

{myProtectionMode = mode;}

setKey()

void SimpleCrypt::setKey

(

quint64

key

)

set Key. setKey

(Re-) initializes the key with the given

• key.

Definition at line 71 of file SimpleCrypt.cpp.

{
    myKey = key;
    splitKey();
}

setMessage()

void SimpleCrypt::setMessage

(

const QString &

thisMessage

)

set Message

set Message. setMessage

Definition at line 320 of file SimpleCrypt.cpp.

{
    if (isDebugMessage)
    {
        qDebug() << thisMessage;
        //std::cout << thisMessage.toStdString() << std::endl;
    }
}

---

The documentation for this class was generated from the following files:

• src/SimpleCrypt.h
• src/SimpleCrypt.cpp