Remove trailing “=” when base64 encoding

Question

I am noticing that whenever I base64 encode a string, a \"=\" is appended at the end. Can I remove this character and then reliably decode it later by adding it back, or is

Answer 1

For Android You may have trouble if You want to use android.util.base64 class, since that don't let you perform UnitTest others that integration test - those uses Adnroid environment.

In other hand if You will use java.util.base64, compiler warns You that You sdk may to to low (below 26) to use it.

So I suggest Android developers to use

implementation "commons-codec:commons-codec:1.13"

Encoding object

fun encodeObjectToBase64(objectToEncode: Any): String{
    val objectJson = Gson().toJson(objectToEncode).toString()
    return encodeStringToBase64(objectJson.toByteArray(Charsets.UTF_8))
}

fun encodeStringToBase64(byteArray: ByteArray): String{
    return Base64.encodeBase64URLSafeString(byteArray).toString() // encode with no padding
}

Decoding to Object

fun <T> decodeBase64Object(encodedMessage: String, encodeToClass: Class<T>): T{
    val decodedBytes = Base64.decodeBase64(encodedMessage)
    val messageString = String(decodedBytes, StandardCharsets.UTF_8)
    return Gson().fromJson(messageString, encodeToClass)
}

Of course You may omit Gson parsing and put straight away into method Your String transformed to ByteArray

Answer 2

= is added for padding. The lenght of a base64 string should be multiple of 4, so 1 or 2 = are added as necessary.

Read: No, you shouldn't remove it.

Answer 3

On Android I am using this:

Global

String CHARSET_NAME ="UTF-8";

Encode

String base64 = new String(
            Base64.encode(byteArray, Base64.URL_SAFE | Base64.NO_PADDING | Base64.NO_CLOSE | Base64.NO_WRAP),
            CHARSET_NAME);
return base64.trim();

Decode

byte[] bytes = Base64.decode(base64String,
            Base64.URL_SAFE | Base64.NO_PADDING | Base64.NO_CLOSE | Base64.NO_WRAP);

equals this on Java:

Encode

private static String base64UrlEncode(byte[] input)
{
    Base64 encoder = new Base64(true);
    byte[] encodedBytes = encoder.encode(input);
    return StringUtils.newStringUtf8(encodedBytes).trim();
}

Decode

private static byte[] base64UrlDecode(String input) {
    byte[] originalValue = StringUtils.getBytesUtf8(input);
    Base64 decoder = new Base64(true);
    return decoder.decode(originalValue);
}

I had never problems with trailing "=" and I am using Bouncycastle as well