RSA encryption differences between Android and Java environments

• Android

First of all, I apologize for the amount of code I'm about to release. I'm trying to use the RSA public key in my java application to encrypt messages in Android applications, and then send the ciphertext back to the Java environment for decryption, but I always receive this error when trying to decrypt:

javax.crypto.BadPaddingException: Decryption error
    at sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:380)
    at sun.security.rsa.RSAPadding.unpad(RSAPadding.java:291)
    at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:356)
    at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:382)
    at javax.crypto.Cipher.doFinal(Cipher.java:2087)
    ...

The ciphertext does contain the correct number of bytes (512), so it is confusing to see the "fill error" exception. Other similar posts on so suggest using "RSA / ECB / pkcs1padding" as the algorithm, but this does not work

What's annoying is that the encryption and decryption in Android environment (using base64.url_safe as' base64type ') works normally. It seems that I can't use the public key generated by Java for initial encryption

I have extracted the smallest code into the example as follows:

Android code

private void exampleMethod(){
    String messageString = "Why does this not work in Android?";

    String serverPubKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoApIBIna77xq4j+M2RmyIhsB++41NHcY4KIPfX4VP4ADnkO+7ejbs4le/twrPtYGESVPF9czSMB5bzmTBZtq0jC8oT/6wiDIBlSuzo4fBrGociBIuaOjyG/j3ZhpcWpWPXuzER+ehuQ+8hZkMuJdK9IodqPR+5jmCef4rXoKObwS02LYQ1co5dEmtZVQRmmeYaVnWibd/s1d4KKGvSzXap3YBTf8peH5UGIQrLOTqvX0bo34xFxmj5U0H3xudnnwuVAlQlj9KiHPPABuwNtm1buRKJb5HZhSCveyT/2YAOmQqGrVN/nALtlZyTDZNs//Vp1zb9exSuG0t5xFc+pn4QIDAQAB";

    String encryptedMessageString = getUrlEncodedCipherText(messageString, serverPubKey, Base64.NO_WRAP);
    /**
     * CipherText is ALWAYS the same and does not decrypt: DA_-RpCki-mjF6tSwiP2IhuW2UfPzZC7A9oVTTNptjT73HtROiQZvUC0Z2veJ5VwVx4toolvLErQmKKoQlqELSD756bu8ohEQwgJ4Xsu-3tXv-uEi5a9a_u19WnNLIF7tayDUhFeD2RzNvW895y1v-D30TvQRskNCFJfnjaytr_vmcVv8HrXURCmG6AMltaqdN72zh8p6VkKcjXSLiCApH957GXSqJCRzxbaQwf8X5EJfn8CQrPDGbE3gdhc2_hFwXQNIdxPxrOLtVbaFp9i_4GRWXJ6E2jHttV2bDv_uSVIz3OBzh7EkJiCnl3c904sH8QZae8c3SQyrTxVL7EpIA,,
     */
}

public static String getUrlEncodedCipherText(String plainText, String pubKey, int base64Type){
    try {
        final PublicKey publicKey = loadPublicKey(pubKey, base64Type);
        final byte[] cipherBytes = encrypt(plainText, publicKey);
        String cipherText = base64Encode(cipherBytes, base64Type);
        String urlEncodedCipherText = urlEncode(cipherText);
        return urlEncodedCipherText;
    }
    catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

public static final String ALGORITHM = "RSA";

public static PublicKey loadPublicKey(String stored, int base64Type) throws GeneralSecurityException {
    String pubKey = stored.replace(BEGIN_PUBLIC_KEY, "");
    pubKey = pubKey.replace(END_PUBLIC_KEY, "");

    byte[] data = Base64.decode(pubKey, base64Type);
    X509EncodedKeySpec spec = new X509EncodedKeySpec(data);
    KeyFactory fact = KeyFactory.getInstance(ALGORITHM);
    PublicKey pub = fact.generatePublic(spec);
    return pub;
}

public static byte[] encrypt(String text, PublicKey key) {
    byte[] cipherText = null;
    try {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        cipherText = cipher.doFinal(text.getBytes());
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return cipherText;
}

public static String base64Encode(byte[] cipherBytes, int base64Type){
    byte[] base64Cipher = Base64.encode(cipherBytes, base64Type);
    return new String(base64Cipher);
}

public static String urlEncode(String text){
    return text.replace("+", "-").replace("/", "_").replace("=", ",");
}

Java code

private void exampleMethod(){
    String pubKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoApIBIna77xq4j+M2RmyIhsB++41NHcY4KIPfX4VP4ADnkO+7ejbs4le/twrPtYGESVPF9czSMB5bzmTBZtq0jC8oT/6wiDIBlSuzo4fBrGociBIuaOjyG/j3ZhpcWpWPXuzER+ehuQ+8hZkMuJdK9IodqPR+5jmCef4rXoKObwS02LYQ1co5dEmtZVQRmmeYaVnWibd/s1d4KKGvSzXap3YBTf8peH5UGIQrLOTqvX0bo34xFxmj5U0H3xudnnwuVAlQlj9KiHPPABuwNtm1buRKJb5HZhSCveyT/2YAOmQqGrVN/nALtlZyTDZNs//Vp1zb9exSuG0t5xFc+pn4QIDAQAB";
    String privKey = "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";

    String message = "Why does this not work in Android?";
    String encryptedMessage = getUrlEncodedCipherText(message, pubKey);

    try {
        byte[] base64Decoded = Base64.decodeBase64(encryptedMessage.getBytes(Charset.forName("UTF-8")));
        String decryptedMessage = decrypt(base64Decoded, loadPrivateKey(privKey));
        System.out.println("decryptedMessage: " + decryptedMessage);
        /**
         * This works! Ciphertext always comes out different, as expected, and decodes successfully.
         */
    }
    catch (Exception e){
        e.printStackTrace();
    }
}

public static String getUrlEncodedCipherText(String plainText, String pubKey){
    try {
        final PublicKey publicKey = loadPublicKey(pubKey);
        final byte[] cipherBytes = encrypt(plainText, publicKey);
        String cipherText = base64Encode(cipherBytes);
        String urlEncodedCipherText = urlEncode(cipherText);
        return urlEncodedCipherText;
    }
    catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

public static final String ALGORITHM = "RSA";

public static PublicKey loadPublicKey(String stored) throws GeneralSecurityException {
    String pubKey = stored.replace(BEGIN_PUBLIC_KEY, "");
    pubKey = pubKey.replace(END_PUBLIC_KEY, "");

    byte[] data = Base64.decodeBase64(pubKey);
    X509EncodedKeySpec spec = new X509EncodedKeySpec(data);
    KeyFactory fact = KeyFactory.getInstance(ALGORITHM);
    PublicKey pub = fact.generatePublic(spec);
    return pub;
}

public static byte[] encrypt(String text, PublicKey key) {
    byte[] cipherText = null;
    try {
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        cipherText = cipher.doFinal(text.getBytes());
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return cipherText;
}

public static String decrypt(byte[] encrypted, PrivateKey key) {
    byte[] decryptedText = null;
    try {
        final Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);
        decryptedText = cipher.doFinal(encrypted);
    }
    catch (Exception e) {
        e.printStackTrace();
        return null;
    }
    return new String(decryptedText);
}

public static String base64Encode(byte[] cipherBytes){
    byte[] base64Cipher = Base64.encodeBase64(cipherBytes);
    return new String(base64Cipher);
}

public static String urlEncode(String text){
    return text.replace("+", "-").replace("/", "_").replace("=", ",");
}

I know that the problem must be different from the way Android and Java interpret RSA algorithm and / or Base64 encoding / decoding, but I'm sorry. Thank you very much for any help

resolvent:

Solved! The problem is that I use the same algorithm string for cipher, keyfactory, etc. I divide it into two different strings. The complete solution to my problem is

Android code

private void exampleMethod(){
    String messageString = "This actually works in Java AND Android!";

    String serverPubKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjS7T3WJ+VLucnUP5WYryeg+hhOjZZl5VxwvJAgo4GrXaXdernTPtmXnOSUlbhd928QRCip7D3rLwJNvGIwhPa6coA+YQnj+aHQC02AvCJP/9jpeNmm5MASZfYFXrdmOrMhAPpDZ4rUk1mqtvpwBkYmW3VbMtG336wT1bAIKPHCZuI2n6glupJvs8gK0NuIoAPRlxiQmQD7NCcRx1Et4JmqOMIRC+HqdGv9GGqC/0PB0Fv6LXi8GdzJQPMdoRLR0rvVykNeIzmcimejoIVjI78XUZeB1hF7p55h6W4C4Xm/PrnzKuXw4lBVehZtRhyIvNO62G/eNEZ3tup1/m+vkzHQIDAQAB";

    String encryptedMessageString = getUrlEncodedCipherText(messageString, serverPubKey, Base64.NO_WRAP);
    System.out.println("encryptedMessageString: " + encryptedMessageString);
    /**
     * This works! Ciphertext always comes out different, as expected, and decodes successfully when fed into Java application.
     */
}

public static String getUrlEncodedCipherText(String plainText, String pubKey, int base64Type){
    try {
        final PublicKey publicKey = loadPublicKey(pubKey, base64Type);
        final byte[] cipherBytes = encrypt(plainText, publicKey);
        String cipherText = base64Encode(cipherBytes, base64Type);
        String urlEncodedCipherText = urlEncode(cipherText);
        return urlEncodedCipherText;
    }
    catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

public static final String ALGORITHM = "RSA";
public static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";

public static PublicKey loadPublicKey(String stored, int base64Type) throws GeneralSecurityException {
    String pubKey = stored.replace(BEGIN_PUBLIC_KEY, "");
    pubKey = pubKey.replace(END_PUBLIC_KEY, "");

    byte[] data = Base64.decode(pubKey, base64Type);
    X509EncodedKeySpec spec = new X509EncodedKeySpec(data);
    KeyFactory fact = KeyFactory.getInstance(ALGORITHM);
    PublicKey pub = fact.generatePublic(spec);
    return pub;
}

public static byte[] encrypt(String text, PublicKey key) {
    byte[] cipherText = null;
    try {
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        cipherText = cipher.doFinal(text.getBytes());
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return cipherText;
}

public static String base64Encode(byte[] cipherBytes, int base64Type){
    byte[] base64Cipher = Base64.encode(cipherBytes, base64Type);
    return new String(base64Cipher);
}

public static String urlEncode(String text){
    return text.replace("+", "-").replace("/", "_").replace("=", ",");
}

Java code

private void exampleMethod(){
    String pubKey = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjS7T3WJ+VLucnUP5WYryeg+hhOjZZl5VxwvJAgo4GrXaXdernTPtmXnOSUlbhd928QRCip7D3rLwJNvGIwhPa6coA+YQnj+aHQC02AvCJP/9jpeNmm5MASZfYFXrdmOrMhAPpDZ4rUk1mqtvpwBkYmW3VbMtG336wT1bAIKPHCZuI2n6glupJvs8gK0NuIoAPRlxiQmQD7NCcRx1Et4JmqOMIRC+HqdGv9GGqC/0PB0Fv6LXi8GdzJQPMdoRLR0rvVykNeIzmcimejoIVjI78XUZeB1hF7p55h6W4C4Xm/PrnzKuXw4lBVehZtRhyIvNO62G/eNEZ3tup1/m+vkzHQIDAQAB";
    String privKey = "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";

    String message = "This actually works in Java AND Android!";
    String encryptedMessage = getUrlEncodedCipherText(message, pubKey);

    try {
        byte[] base64Decoded = Base64.decodeBase64(encryptedMessage.getBytes(Charset.forName("UTF-8")));
        String decryptedMessage = decrypt(base64Decoded, loadPrivateKey(privKey));
        System.out.println("decryptedMessage: " + decryptedMessage);
        /**
         * This works! Ciphertext always comes out different, as expected, and decodes successfully.
         */
    }
    catch (Exception e){
        e.printStackTrace();
    }
}

public static String getUrlEncodedCipherText(String plainText, String pubKey){
    try {
        final PublicKey publicKey = loadPublicKey(pubKey);
        final byte[] cipherBytes = encrypt(plainText, publicKey);
        String cipherText = base64Encode(cipherBytes);
        String urlEncodedCipherText = urlEncode(cipherText);
        return urlEncodedCipherText;
    }
    catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

public static final String ALGORITHM = "RSA";
public static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";

public static PublicKey loadPublicKey(String stored) throws GeneralSecurityException {
    String pubKey = stored.replace(BEGIN_PUBLIC_KEY, "");
    pubKey = pubKey.replace(END_PUBLIC_KEY, "");

    byte[] data = Base64.decodeBase64(pubKey);
    X509EncodedKeySpec spec = new X509EncodedKeySpec(data);
    KeyFactory fact = KeyFactory.getInstance(ALGORITHM);
    PublicKey pub = fact.generatePublic(spec);
    return pub;
}

public static byte[] encrypt(String text, PublicKey key) {
    byte[] cipherText = null;
    try {
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        cipherText = cipher.doFinal(text.getBytes());
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return cipherText;
}

public static String decrypt(byte[] encrypted, PrivateKey key) {
    byte[] decryptedText = null;
    try {
        final Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);
        decryptedText = cipher.doFinal(encrypted);
    }
    catch (Exception e) {
        e.printStackTrace();
        return null;
    }
    return new String(decryptedText);
}

public static String base64Encode(byte[] cipherBytes){
    byte[] base64Cipher = Base64.encodeBase64(cipherBytes);
    return new String(base64Cipher);
}

public static String urlEncode(String text){
    return text.replace("+", "-").replace("/", "_").replace("=", ",");
}

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