Im trying to implement AES in an Android application. The server is a PHP server.
This is the AES code :
public class AES{
private String SecretKey = "89432hjfsd891787";
private String iv = "fedcba9876543210";
private IvParameterSpec ivspec;
private SecretKeySpec keyspec;
private Cipher cipher;
public AES()
{
ivspec = new IvParameterSpec(iv.getBytes());
keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");
try {
cipher = Cipher.getInstance("AES/CBC/NoPadding");
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public byte[] encrypt(String text) throws Exception
{
if(text == null || text.length() == 0)
throw new Exception("Empty string");
byte[] encrypted = null;
try {
cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);
encrypted = cipher.doFinal(padString(text).getBytes());
} catch (Exception e)
{
throw new Exception("[encrypt] " + e.getMessage());
}
return encrypted;
}
public byte[] decrypt(String code) throws Exception
{
if(code == null || code.length() == 0)
throw new Exception("Empty string");
byte[] decrypted = null;
try {
cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);
decrypted = cipher.doFinal(hexToBytes(code));
} catch (Exception e)
{
throw new Exception("[decrypt] " + e.getMessage());
}
return decrypted;
}
public static String bytesToHex(byte[] data)
{
if (data==null)
{
return null;
}
int len = data.length;
String str = "";
for (int i=0; i<len; i++) {
if ((data[i]&0xFF)<16)
str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
else
str = str + java.lang.Integer.toHexString(data[i]&0xFF);
}
return str;
}
public static byte[] hexToBytes(String str) {
if (str==null) {
return null;
} else if (str.length() < 2) {
return null;
} else {
int len = str.length() / 2;
byte[] buffer = new byte[len];
for (int i=0; i<len; i++) {
buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
}
return buffer;
}
}
private static String padString(String source)
{
char paddingChar = ' ';
int size = 16;
int x = source.length() % size;
int padLength = size - x;
for (int i = 0; i < padLength; i++) {
source += paddingChar;
}
return source;
}
}
I get an error while decrypting the incoming string : Cipher functions:EVP_DecryptFinal_ex:DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
How do i go about this?
Manually padding the String representation of the plaintext with spaces is not a good padding mechanism. Instead, you should use AES/CBC/PKCS5Padding which will handle the padding as prescribed in PKCS #5/#7.
You should also:
generate a unique IV per encryption operation rather than re-using the same value for all messages
Use an authenticated mode of operation (GCM, HMAC/SHA-256 MAC over cipher text, etc.)
Store the key in hexadecimal representation of the raw bytes rather than an ASCII/UTF-8 String encoding (not specified in your code)
Encode the cipher text in Base64 or Hex before serializing/transmitting. Encoding errors can contribute to padding exceptions during decryption.
Related
I am new to Android-Java. I have below function in C# for Encryption (Triple DES)
public string Encrypt(string data)
{
try
{
if (!string.IsNullOrEmpty(data))
{
//byte[] keyArray;
byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(data);
//System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();
byte[] keyArray = UTF8Encoding.UTF8.GetBytes(key);
TripleDESCryptoServiceProvider CryptDesECB = new TripleDESCryptoServiceProvider();
CryptDesECB.Key = keyArray;
CryptDesECB.Mode = CipherMode.ECB;
CryptDesECB.Padding = PaddingMode.PKCS7;
ICryptoTransform cTransform = CryptDesECB.CreateEncryptor();
byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
CryptDesECB.Clear();
return Convert.ToBase64String(resultArray, 0, resultArray.Length);
}
return string.Empty;
}
catch (Exception)
{
return string.Empty;
}
}
I have tried below code for having same Encryption function in Android platform:
public static String EncryptText(String message) throws Exception {
MessageDigest md = MessageDigest.getInstance("SHA-1");
byte[] digestOfPassword = md.digest(secretKey.getBytes("utf-8"));
byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
SecretKey key = new SecretKeySpec(keyBytes, "DESede");
Cipher cipher = Cipher.getInstance("DESede");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] plainTextBytes = message.getBytes("utf-8");
byte[] buf = cipher.doFinal(plainTextBytes);
byte [] base64Bytes = Base64.encode(buf,Base64.DEFAULT);
String base64EncryptedString = new String(base64Bytes);
return base64EncryptedString;
}
But, the encryption result is different on both platforms? If anyone can help me in pointing the issue in Android function.
Thanks in advance.
I wrote below class for Triple DES ECB mode PKCS5/7 padding mode encryption-decryption and it worked for me:
public class DESedeEncryption {
private static final String UNICODE_FORMAT = "UTF8";
public static final String DESEDE_ENCRYPTION_SCHEME = "DESede";
private KeySpec myKeySpec;
private SecretKeyFactory mySecretKeyFactory;
private Cipher cipher;
byte[] keyAsBytes;
private String myEncryptionKey;
private String myEncryptionScheme;
SecretKey key;
public DESedeEncryption() throws Exception
{
myEncryptionKey = "YOURPRIVATEKEY";
myEncryptionScheme = DESEDE_ENCRYPTION_SCHEME;
keyAsBytes = myEncryptionKey.getBytes(UNICODE_FORMAT);
myKeySpec = new DESedeKeySpec(keyAsBytes);
mySecretKeyFactory = SecretKeyFactory.getInstance(myEncryptionScheme);
cipher = Cipher.getInstance(myEncryptionScheme);
key = mySecretKeyFactory.generateSecret(myKeySpec);
}
/**
* Method To Encrypt The String
*/
public String encrypt(String unencryptedString) {
String encryptedString = null;
try {
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] plainText = unencryptedString.getBytes(UNICODE_FORMAT);
byte[] encryptedText = cipher.doFinal(plainText);
encryptedString = Base64.encodeToString(encryptedText, Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
}
return encryptedString.endsWith("\n") ? encryptedString.replace("\n","") : encryptedString;
}
/**
* Method To Decrypt An Ecrypted String
*/
public String decrypt(String encryptedString) {
String decryptedText=null;
try {
cipher.init(Cipher.DECRYPT_MODE, key);
byte[] encryptedText = Base64.decode(encryptedString, Base64.DEFAULT);
byte[] plainText = cipher.doFinal(encryptedText);
decryptedText= bytes2String(plainText);
} catch (Exception e) {
e.printStackTrace();
}
return decryptedText;
}
/**
* Returns String From An Array Of Bytes
*/
private static String bytes2String(byte[] bytes) {
StringBuffer stringBuffer = new StringBuffer();
for (int i = 0; i > bytes.length; i++) {
stringBuffer.append((char) bytes[i]);
}
return stringBuffer.toString();
}
}
I've been working on it for several days but without success, I' m doing SMS encryption in android using RSA encryption, the problem is how can I convert a String to public key and use it for encryption, I'm sending the publicKey converted into String via SMS but I'm not able to get the key back.
This is how my algorithm works but when I send "puk" as a string via Sms and make encryption it doesn't work anymore!!! plz help me . . .
private final static String RSA = "RSA";
public static PublicKey uk;
public static PrivateKey rk;
public static String puk;
public static void generateKey() throws Exception
{
KeyPairGenerator gen = KeyPairGenerator.getInstance(RSA);
gen.initialize(128, new SecureRandom());
KeyPair keyPair = gen.generateKeyPair();
uk = keyPair.getPublic();
rk = keyPair.getPrivate();
puk = uk.toString();
}
private static byte[] encrypt(String text, PublicKey pubRSA) throws Exception
{
Cipher cipher = Cipher.getInstance(RSA);
cipher.init(Cipher.ENCRYPT_MODE, pubRSA);
return cipher.doFinal(text.getBytes());
}
public final static String encrypt(String text)
{
try {
return byte2hex(encrypt(text, uk));
}
catch(Exception e)
{
e.printStackTrace();
}
return null;
}
public final static String decrypt(String data)
{
try{
String text = new String(decrypt(hex2byte(data.getBytes())));
return text+" OK";
}
catch (Exception e)
{
return "Error: "+e;
}
}
private static byte[] decrypt(byte[] src) throws Exception
{
Cipher cipher = Cipher.getInstance(RSA);
cipher.init(Cipher.DECRYPT_MODE, rk);
return cipher.doFinal(src);
}
public static String byte2hex(byte[] b)
{
String hs = "";
String stmp = "";
for (int n = 0; n < b.length; n ++)
{
stmp = Integer.toHexString(b[n] & 0xFF);
if (stmp.length() == 1)
hs += ("0" + stmp);
else
hs += stmp;
}
return hs.toUpperCase();
}
public static byte[] hex2byte(byte[] b)
{
if ((b.length % 2) != 0)
throw new IllegalArgumentException("hello");
byte[] b2 = new byte[b.length / 2];
for (int n = 0; n < b.length; n += 2)
{
String item = new String(b, n, 2);
b2[n/2] = (byte)Integer.parseInt(item, 16);
}
return b2;
}
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
Closed 9 years ago.
i want to implement the AES techniques in java for android application, i search out many tutorial for this but that was not super. SO please help in this regard, if some body know the code, for Implementing AES techniques for ANDROID APPLICATION.
thanks in adnvance.
Aes ecrpt class
package com.d.social.network;
import java.security.NoSuchAlgorithmException;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
public class MCrypt {
private String iv = "fedcba9876543210";//Dummy iv (CHANGE IT!)
private IvParameterSpec ivspec;
private SecretKeySpec keyspec;
private Cipher cipher;
private String SecretKey = "0123456789abcdef";//Dummy secretKey (CHANGE IT!)
public MCrypt()
{
ivspec = new IvParameterSpec(iv.getBytes());
keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");
try {
cipher = Cipher.getInstance("AES/CBC/NoPadding");
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public byte[] encrypt(String text) throws Exception
{
if(text == null || text.length() == 0)
throw new Exception("Empty string");
byte[] encrypted = null;
try {
cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);
encrypted = cipher.doFinal(padString(text).getBytes());
} catch (Exception e)
{
throw new Exception("[encrypt] " + e.getMessage());
}
return encrypted;
}
public byte[] decrypt(String code) throws Exception
{
if(code == null || code.length() == 0)
throw new Exception("Empty string");
byte[] decrypted = null;
try {
cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);
decrypted = cipher.doFinal(hexToBytes(code));
if( decrypted.length > 0)
{
int trim = 0;
for( int i = decrypted.length - 1; i >= 0; i-- ) if( decrypted[i] == 0 ) trim++;
if( trim > 0 )
{
byte[] newArray = new byte[decrypted.length - trim];
System.arraycopy(decrypted, 0, newArray, 0, decrypted.length - trim);
decrypted = newArray;
}
}
} catch (Exception e)
{
throw new Exception("[decrypt] " + e.getMessage());
}
return decrypted;
}
public static String bytesToHex(byte[] data)
{
if (data==null)
{
return null;
}
int len = data.length;
String str = "";
for (int i=0; i<len; i++) {
if ((data[i]&0xFF)<16)
str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
else
str = str + java.lang.Integer.toHexString(data[i]&0xFF);
}
return str;
}
public static byte[] hexToBytes(String str) {
if (str==null) {
return null;
} else if (str.length() < 2) {
return null;
} else {
int len = str.length() / 2;
byte[] buffer = new byte[len];
for (int i=0; i<len; i++) {
buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
}
return buffer;
}
}
private static String padString(String source)
{
char paddingChar = ' ';
int size = 16;
int x = source.length() % size;
int padLength = size - x;
for (int i = 0; i < padLength; i++)
{
source += paddingChar;
}
return source;
}
}
To use it
MCrypt mcrypt = new MCrypt();
MCrypt.bytesToHex( mcrypt.encrypt("hello"));
So i have this code here;
myIntent.putExtra("schedule",serializableClass);
and this intent goes to my Broadcast Reciever and i did get that serializable as below,
public void onRecieve(Context context, Intent intent)
{
Schedule s = (Schedule) intent.getSerializableExtra("schedule");
}
but it always returns even though when i put the Extras its not null, even checked before passing it on myIntent.putExtra() i really don't know what happen returns, why does it always returns null?.. anyone knows this problem?
The cast is wrong, i would be more easier to pass the serialized string and do deserialization. I' m using this class.
public final class ObjectSerializer {
private ObjectSerializer() {
}
public static String serialize(Serializable obj) throws IOException {
if (obj == null)
return "";
try {
ByteArrayOutputStream serialObj = new ByteArrayOutputStream();
ObjectOutputStream objStream = new ObjectOutputStream(serialObj);
objStream.writeObject(obj);
objStream.close();
return encodeBytes(serialObj.toByteArray());
} catch (Exception e) {
throw new IOException("Serialization error: " + e.getMessage(), e);
}
}
public static Object deserialize(String str) throws IOException {
if (str == null || str.length() == 0)
return null;
try {
ByteArrayInputStream serialObj = new ByteArrayInputStream(
decodeBytes(str));
ObjectInputStream objStream = new ObjectInputStream(serialObj);
return objStream.readObject();
} catch (Exception e) {
throw new IOException("Serialization error: " + e.getMessage(), e);
}
}
public static String encodeBytes(byte[] bytes) {
StringBuffer strBuf = new StringBuffer();
for (int i = 0; i < bytes.length; i++) {
strBuf.append((char) (((bytes[i] >> 4) & 0xF) + ('a')));
strBuf.append((char) (((bytes[i]) & 0xF) + ('a')));
}
return strBuf.toString();
}
public static byte[] decodeBytes(String str) {
byte[] bytes = new byte[str.length() / 2];
for (int i = 0; i < str.length(); i += 2) {
char c = str.charAt(i);
bytes[i / 2] = (byte) ((c - 'a') << 4);
c = str.charAt(i + 1);
bytes[i / 2] += (c - 'a');
}
return bytes;
}
}
after that use like this:
String scheduleSerialization = ObjectSerializer.serialize(schedule);
myIntent.putExtra("schedule",scheduleSerialization);
the last thing to do is:
public void onRecieve(Context context, Intent intent)
{
String serial = intent.getStringExtra("schedule");
if(serial!=null)
Schedule s = (Schedule) ObjectSerializer.deserialize(serial) ;
}
Using Serializable on Android is discouraged because it is slow. If you look at the android source code you will see that
the usually break down the information into multiple keys and send them as primitive types (Integer, String, etc..)
when that can't be done, the will use a Parcelable object
For downloading stuff I work with the apache classes HTTPResponse HTTPClient etc.
I check for a valid download like this:
entity.writeTo(new FileOutputStream(outfile));
if(outfile.length()!=entity.getContentLength()){
long fileLength = outfile.length();
outfile.delete();
throw new Exception("Incomplete download, "+fileLength+"/"
+entity.getContentLength()+" bytes downloaded");
}
But it seems that the exception is never triggered. How to properly handle this? Is entity.getContentLength the length of the file on server or the amount of data received?
The file request should always come with a MD5 checksum. If you have an MD5 header then all you need to do is check that against the files generated MD5. Then your done, its better to do it this way as you can have a file with the same number of bytes but one byte gets garbled in transmission.
entity.writeTo(new FileOutputStream(outfile));
String md5 = response.getHeaders("Content-MD5")[0].getValue();
byte[] b64 = Base64.decode(md5, Base64.DEFAULT);
String sB64 = IntegrityUtils.toASCII(b64, 0, b64.length);
if (outfile.exists()) {
String orgMd5 = null;
try {
orgMd5 = IntegrityUtils.getMD5Checksum(outfile);
} catch (Exception e) {
Log.d(TAG,"Exception in file hex...");
}
if (orgMd5 != null && orgMd5.equals(sB64)) {
Log.d(TAG,"MD5 is equal to files MD5");
} else {
Log.d(TAG,"MD5 does not equal files MD5");
}
}
Add this class to your project:
public class IntegrityUtils {
public static String toASCII(byte b[], int start, int length) {
StringBuffer asciiString = new StringBuffer();
for (int i = start; i < (length + start); i++) {
// exclude nulls from the ASCII representation
if (b[i] != (byte) 0x00) {
asciiString.append((char) b[i]);
}
}
return asciiString.toString();
}
public static String getMD5Checksum(File file) throws Exception {
byte[] b = createChecksum(file);
String result = "";
for (int i = 0; i < b.length; i++) {
result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
}
return result;
}
public static byte[] createChecksum(File file) throws Exception {
InputStream fis = new FileInputStream(file);
byte[] buffer = new byte[1024];
MessageDigest complete = MessageDigest.getInstance("MD5");
int numRead;
do {
numRead = fis.read(buffer);
if (numRead > 0) {
complete.update(buffer, 0, numRead);
}
} while (numRead != -1);
fis.close();
return complete.digest();
}
}