Implementing AES encryption in Android
MSR
I found this Java AES encryption on the internet. Can I modify and use this Java code in an Android application? Actually I don't know if it will fit my android device. If it can be used, does it mean that this Java code can be modified?
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;
/**
Aes encryption
*/
public class AES
{
private static SecretKeySpec secretKey ;
private static byte[] key ;
private static String decryptedString;
private static String encryptedString;
public static void setKey(String myKey){
MessageDigest sha = null;
try {
key = myKey.getBytes("UTF-8");
System.out.println(key.length);
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
System.out.println(key.length);
System.out.println(new String(key,"UTF-8"));
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static String getDecryptedString() {
return decryptedString;
}
public static void setDecryptedString(String decryptedString) {
AES.decryptedString = decryptedString;
}
public static String getEncryptedString() {
return encryptedString;
}
public static void setEncryptedString(String encryptedString) {
AES.encryptedString = encryptedString;
}
public static String encrypt(String strToEncrypt)
{
try
{
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
setEncryptedString(Base64.encodeBase64String(cipher.doFinal(strToEncrypt.getBytes("UTF-8"))));
}
catch (Exception e)
{
System.out.println("Error while encrypting: "+e.toString());
}
return null;
}
public static String decrypt(String strToDecrypt)
{
try
{
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
setDecryptedString(new String(cipher.doFinal(Base64.decodeBase64(strToDecrypt))));
}
catch (Exception e)
{
System.out.println("Error while decrypting: "+e.toString());
}
return null;
}
public static void main(String args[])
{
final String strToEncrypt = "My text to encrypt";
final String strPssword = "encryptor key";
AES.setKey(strPssword);
AES.encrypt(strToEncrypt.trim());
System.out.println("String to Encrypt: " + strToEncrypt);
System.out.println("Encrypted: " + AES.getEncryptedString());
final String strToDecrypt = AES.getEncryptedString();
AES.decrypt(strToDecrypt.trim());
System.out.println("String To Decrypt : " + strToDecrypt);
System.out.println("Decrypted : " + AES.getDecryptedString());
}
}
Source : http://aesencryption.net/ _
Shatney
When I implement AES encryption in an android application, I have to specify the provider BouncyCastle when instantiating the cipher.
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding","BC");
You should consider using cbc mode as ecb mode is not really secure.
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding","BC");
With a slight modification to your code, this should work:
import android.util.Base64;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Random;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
/**
Aes encryption
*/
public class AES
{
private static SecretKeySpec secretKey ;
private static byte[] key ;
private static byte[] iv;
private static String decryptedString;
private static String encryptedString;
public static void setKey(String myKey){
MessageDigest sha = null;
try {
key = myKey.getBytes("UTF-8");
System.out.println(key.length);
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
secretKey = new SecretKeySpec(key, "AES");
iv = new byte[]{11,53,63,87,11,69,63,28,0,9,18,99,95,23,45,8};
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static String getDecryptedString() {
return decryptedString;
}
public static void setDecryptedString(String decryptedString) {
AES.decryptedString = decryptedString;
}
public static String getEncryptedString() {
return encryptedString;
}
public static void setEncryptedString(String encryptedString) {
AES.encryptedString = encryptedString;
}
public static String encrypt(String strToEncrypt)
{
try
{
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
cipher.init(Cipher.ENCRYPT_MODE, secretKey,new IvParameterSpec(iv));
setEncryptedString(Base64.encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")),Base64.DEFAULT));
}
catch (Exception e)
{
System.out.println("Error while encrypting: "+e.toString());
}
return null;
}
public static String decrypt(String strToDecrypt)
{
try
{
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7PADDING","BC");
cipher.init(Cipher.DECRYPT_MODE, secretKey,new IvParameterSpec(iv));
String decoded = new String(cipher.doFinal(Base64.decode(strToDecrypt,Base64.DEFAULT)), Charset.forName("UTF-8"));
setDecryptedString(decoded);
}
catch (Exception e)
{
System.out.println("Error while decrypting: "+e.toString());
}
return null;
}
}