AES Encryption-Rijndael Block Cipher to Symbian OS
This code snippet provides an implementation of the AES Encryption-Rijndael Block Cipher on Symbian. The implementation can be used for encrypting/decrypting on Symbian, but if you want to decrypt on another platform you should encrypt using the Symbian Cryptography APIs .
Article Metadata
Rijndael Symbian OS Interface
#include "rijndael-alg-symbianos.h"
namespace aes {
/* Modes */
#define DIR_ENCRYPT 0 // Encrypting?
#define DIR_DECRYPT 1 // Decrypting?
#define MODE_ECB 1 // Ciphering in ECB?
#define MODE_CBC 2 // Ciphering in CBC?
#define MODE_CFB1 3 // Ciphering in 1-bit CFB?
/* Block Size */
#define BITSPERBLOCK 128 // Bits in a cipher block
/* Error Codes */
#define BAD_KEY_DIR -1 // Key direction is invalid
#define BAD_KEY_MAT -2 // Key not of correct length
#define BAD_KEY_INSTANCE -3 // Key is not valid
#define BAD_CIPHER_MODE -4 // Cipher instance invalid
#define BAD_CIPHER_STATE -5 // Cipher in wrong state
#define BAD_CIPHER_INSTANCE -7
/* Keys */
#define MAX_KEY_SIZE 64 // # of ASCII char's of a key
#define MAX_IV_SIZE BITSPERBLOCK/8 // # bytes of an IV
/* The structure for key information */
typedef struct {
TUint8 direction; // Encrypting or decrypting?
TInt keyLen; // Length of the key
TText8 keyMaterial[MAX_KEY_SIZE+1]; // Raw key
TInt blockLen; // Block Length
word8 keySched[MAXROUNDS+1][4][MAXBC];
} keyInstance;
/* The structure for cipher information */
typedef struct {
TUint8 mode; // MODE_ECB, MODE_CBC, or MODE_CFB1
TUint8 IV[MAX_IV_SIZE]; // Initialization vector
TInt blockLen;
} cipherInstance;
/* ********* */
/* Functions */
/* ********* */
TInt makeKey(keyInstance *key,
TUint8 direction,
TInt keyLen,
const TText8 *keyMaterial);
TInt cipherInit(cipherInstance *cipher,
TUint8 mode,
const TText8 *IV);
TInt blockEncrypt(const cipherInstance *cipher,
keyInstance *key,
TUint8 *input,
TInt inputLen,
TUint8 *outBuffer);
TInt blockDecrypt(const cipherInstance *cipher,
keyInstance *key,
TUint8 *input,
TInt inputLen,
TUint8 *outBuffer);
TInt cipherUpdateRounds(const cipherInstance *cipher,
keyInstance *key,
TUint8 *input,
TInt inputLen,
TUint8 *outBuffer,
TInt Rounds);
} // namespace aes
Working with Rijndael
// Secret message (which fits exactly in one block)
_LIT8(KMySecret, "Hello world!!!!!");
TBuf8<128> secret(KMySecret);
//
// Init stuff
TUint8 block[4*MAXBC];
TPtr8 blockPtr(block, BITSPERBLOCK/8);
aes::keyInstance keyInst;
aes::cipherInstance cipherInst;
//
// Generate key instance for encryption.
// The secret key material is an hex string
// with a length of keyLen/4 bytes.
TInt keyLen = 128;
TText8* secretKeyMaterial =
(TText8*) "E5E6E7E9EA292A2B2D256789012345E5";
keyInst.blockLen = BITSPERBLOCK;
aes::makeKey(&keyInst, DIR_ENCRYPT,
keyLen, secretKeyMaterial);
//
// Init cipher instance
cipherInst.blockLen = BITSPERBLOCK;
aes::cipherInit(&cipherInst, MODE_ECB, NULL);
//
// Encrypt block
// Fill block with our secret message
blockPtr.Append(secret.Ptr(), BITSPERBLOCK/8);
aes::blockEncrypt(&cipherInst, &keyInst,
block, BITSPERBLOCK, block);
TBuf8<BITSPERBLOCK/8> cipherText;
cipherText.Append(blockPtr);
blockPtr.Zero();
//
// cipherText contains the encrypted secret
//
// Generate key instance for decryption
keyInst.blockLen = BITSPERBLOCK;
aes::makeKey(&keyInst, DIR_DECRYPT,
keyLen, secretKeyMaterial);
//
// Init cipher instance
cipherInst.blockLen = BITSPERBLOCK;
aes::cipherInit(&cipherInst, MODE_ECB, NULL);
//
// Decrypt block
blockPtr.Append(cipherText.Ptr(), BITSPERBLOCK/8);
aes::blockDecrypt(&cipherInst, &keyInst,
block, BITSPERBLOCK, block);
TBuf8<BITSPERBLOCK/8> decryptedText;
decryptedText.Append(blockPtr);
//
// decryptedText contains "Hello world!!!!!"
20 Sep
2009
This article describes how to use Rijndael Block Cipher to Symbian OS with Symbian C++. Cryptography with this cypher is illustrated in detail. Cryptography is the study of hidden/ secret information. Encryption is the process of hiding information to make it unreadable except those who knows the special "key". And the process of getting the hidden information back i.e. to make it readable is called decryption.
The code snippest presents an example which encrypts and decrypts "Hello World" with the mentioned cypher. The code for the class declaration and cpp file is illustrated in this article with required comments-which makes them understandable.
The Cryptography presented here can only be performed on S60 platform and not meant for cross-platform. This article can be useful to beginners and intermediate developers to study cryptography.