Android Encrypting String using RSA Public key

Question

I am working in a project where I have to encrypt password using RSA public key. I tried many samples and solutions from SO like as follows

But none of the solutions worked in my case unfortunately. I was getting following exceptions repeatedly if i try with any work around

Error Log:

04-21 07:50:57.876 18842-18842/com.takeoffandroid.passwordencryption W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
04-21 07:50:57.986 18842-18842/com.takeoffandroid.passwordencryption W/System.err: java.security.spec.InvalidKeySpecException: java.lang.RuntimeException: error:0c0890ba:ASN.1 encoding routines:asn1_check_tlen:WRONG_TAG
04-21 07:50:57.986 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.org.conscrypt.OpenSSLKey.getPublicKey(OpenSSLKey.java:250)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.org.conscrypt.OpenSSLRSAKeyFactory.engineGeneratePublic(OpenSSLRSAKeyFactory.java:47)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at java.security.KeyFactory.generatePublic(KeyFactory.java:172)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.takeoffandroid.passwordencryption.MainActivity.RSAEncrypt(MainActivity.java:181)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.takeoffandroid.passwordencryption.MainActivity.onCreate(MainActivity.java:80)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.Activity.performCreate(Activity.java:6532)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2383)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2490)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.ActivityThread.access$900(ActivityThread.java:157)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.os.Looper.loop(Looper.java:148)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5437)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err: Caused by: java.lang.RuntimeException: error:0c0890ba:ASN.1 encoding routines:asn1_check_tlen:WRONG_TAG
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.org.conscrypt.NativeCrypto.d2i_PUBKEY(Native Method)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:     at com.android.org.conscrypt.OpenSSLKey.getPublicKey(OpenSSLKey.java:248)
04-21 07:50:57.987 18842-18842/com.takeoffandroid.passwordencryption W/System.err:  ... 16 more

My Requirement:

I have a public key with me and I wanted to encrypt the text entered in the edittext with that public key. For Eg: Password@123 should be encrypted using public key.

Public Key:

public static String PUBLIC_KEY = "-----BEGIN RSA PUBLIC KEY-----\n" +
            "MMDDFDFK43545mmdf499Mdfdasl43ND/GGKLGKL4434safddEcBFfbTZUM517\n" +
            "VDSVFS45fwdGJGGLKGGL332XSA3=d/S/2ETegJPFQ4sjiY7/DsS2o9Gr\n" +
            "asBASF3465243FCDXSDCDxsSFC39NkDiNO2QKNXivAQVpuJeuoDeK\n" +
            "wNGmwDkIsvxBn8u55QpOwvdaRBeLqllJ6xoF6OuwnD0IB4tVDL2MbMVj1U9GtEGL\n" +
            "DJKHSJAH434jjhdds54KkhjbvGJGGGG/Vn4OYNooIWE9uuiyxm2M\n" +
            "AFSDAFXZB546FGHxcvv324FDGJIYTaa346/9xQIDAQAB\n" +
            "-----END RSA PUBLIC KEY-----";

Code Implementations I tried:

Sample I:

  public static String encryptDataRSA(final String data) throws IOException {
        final byte[] dataToEncrypt = data.getBytes();
        byte[] encryptedData = null;

        try {

            PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(RSAUtils.PUBLIC_KEY.getBytes()));

            final Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            encryptedData = cipher.doFinal(dataToEncrypt);

            try {
                final String encryptedText = new String(Base64.encode(encryptedData, Base64.DEFAULT), "UTF-8");
                return encryptedText.toString();
            }
            catch (final UnsupportedEncodingException e1) { return null; }
        } catch (Exception e) { e.printStackTrace(); }

        return "ERROR";
    }

Sample II:

    public byte[] RSAEncrypt(final String plain) throws NoSuchAlgorithmException, NoSuchPaddingException,
            InvalidKeyException, IllegalBlockSizeException, BadPaddingException, InvalidKeySpecException {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
        kpg.initialize(1024);
        KeyPair kp = kpg.genKeyPair();
        PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(RSAUtils.PUBLIC_KEY.getBytes()));

        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] encryptedBytes = cipher.doFinal(plain.getBytes());
        System.out.println("EEncrypted?????" + org.apache.commons.codec.binary.Hex.encodeHexString(encryptedBytes));
        return encryptedBytes;
    }

Sample III:

 public static String encryptRSAToString(String text, String strPublicKey) {
        byte[] cipherText = null;
        String strEncryInfoData="";
        try {

            KeyFactory keyFac = KeyFactory.getInstance("RSA");
            KeySpec keySpec = new X509EncodedKeySpec(Base64.decode(strPublicKey.trim().getBytes(), Base64.DEFAULT));
            Key publicKey = keyFac.generatePublic(keySpec);

            // get an RSA cipher object and print the provider
            final Cipher cipher = Cipher.getInstance("RSA");
            // encrypt the plain text using the public key
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            cipherText = cipher.doFinal(text.getBytes());
            strEncryInfoData = new String(Base64.encode(cipherText,Base64.DEFAULT));

        } catch (Exception e) {
            e.printStackTrace();
        }
        return strEncryInfoData.replaceAll("(\\r|\\n)", "");
    }

Any help or suggestions would be really helpful to me. Thanks in advance.

Your public key is clearly corrupted. You have an equals sign ('=') in the middle of the base64 string which is invalid. Even if I remove that the key is still invalid. — President James K. Polk
– President James K. Polk, Commented Apr 21, 2017 at 11:53
Actually i posted a sample public key. The actual key which I am using is completely different. — Chandru
– Chandru, Commented Apr 22, 2017 at 3:22
@JamesKPolk Please find the actual key here pastebin.com/7beLfTpK — Chandru
– Chandru, Commented Apr 22, 2017 at 3:23

Israel · Accepted Answer · 2017-04-21 22:51:05Z

21

try this.

public static String PUBLIC_KEY = "YOUR PUBLIC KEY";

static String enccriptData(String txt)
{
  String encoded = "";
  byte[] encrypted = null;
    try {
        byte[] publicBytes = Base64.decode(PUBLIC_KEY, Base64.DEFAULT);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey pubKey = keyFactory.generatePublic(keySpec);
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING"); //or try with "RSA"
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        encrypted = cipher.doFinal(txt.getBytes());
        encoded = Base64.encodeToString(encrypted, Base64.DEFAULT);
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return encoded;
}

EDIT:

You can use my code but read the comment of James K Polk, he's right

edited Apr 21, 2017 at 22:51

answered Apr 21, 2017 at 4:35

Israel

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8 Comments

Chandru Over a year ago

Thanks for replying. Again I got the following exception

Israel Over a year ago

You put the key as in the example? X509EncodedKeySpec expects DER encoded data not PEM The code works correctly for me. .

Israel Over a year ago

please, don't publish your private key. In your code, you have a key: public static String PUBLIC_KEY = "-----BEGIN RSA PUBLIC KEY-----\n" + "MMDDFDFK43545mmdf499Mdfdasl43ND/GGKLGKL4434safddEcBFfbTZUM517\n" +..... Place it on a single line without -----BEGIN RSA PUBLIC KEY----, -----END RSA PUBLIC KEY----- and \n Like that of my example: public static String PUBLIC_KEY = "MMDDFDFK43545mmdf499Mdfdasl43ND.......";

Gweltaz Niquel Over a year ago

@Israel It's public key, not private. No matter distributing it there is no secret in it as it's RSA algorithm.

Akshay Sahai Over a year ago

@Israel, Dude! you are awesome.

|

Mohammad Mirzakhani · Accepted Answer · 2020-12-01 16:40:23Z

The Kotlin Code for RSA encryption:

first of all you need to remove "-----BEGIN PUBLIC KEY-----" and "-----END PUBLIC KEY-----" and ... to have a clean text.

Just use this:

 publicKy = publicKy  .replace("\\r".toRegex(), "")
        .replace("\\n".toRegex(), "")
        .replace(System.lineSeparator().toRegex(), "")
        .replace("-----BEGIN PUBLIC KEY-----", "")
        .replace("-----END PUBLIC KEY-----", "")


    val encryptedString = enccriptData(input,publicKy)

' input ' is the text which you want to encrypt with your public key,
then you need to use this method:

fun enccriptData(txt: String, pk: String): String? {
    var encoded = ""
    var encrypted: ByteArray? = null
    try {
        val publicBytes: ByteArray = Base64.decode(pk, Base64.DEFAULT)
        val keySpec = X509EncodedKeySpec(publicBytes)
        val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")
        val pubKey: PublicKey = keyFactory.generatePublic(keySpec)
        val cipher: Cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING")
        cipher.init(Cipher.ENCRYPT_MODE, pubKey)
        encrypted = cipher.doFinal(txt.toByteArray())
        encoded = Base64.encodeToString(encrypted, Base64.DEFAULT)
    } catch (e: Exception) {
        e.printStackTrace()
    }
    return encoded
}

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