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Revision as of 22:11, 22 February 2012 by vineet.jain (Talk | contribs)

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AES Encryption-Rijndael Block Cipher to Symbian OS

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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 .

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Created: giridharn (24 May 2007)
Last edited: vineet.jain (22 Feb 2012)

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!!!!!"
This page was last modified on 22 February 2012, at 22:11.
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