How to read an encrypted Realm Database Android

Question

I'm having some problems to access an encrypted Realm DB. This is my flow: - iOS team create the encrypted DB - they created the key - then I receive the key in a API response to avoid store the key locally.

When receive the key I convert it to SHA-512 with the following method:

fun String.getSHA512Pass(): String {
return MessageDigest
    .getInstance("SHA-512")
    .digest(this.toByteArray())
    .fold("", { str, it -> str + "%02x".format(it) })}

And then I just Apply it to my RealmConfiguration:

class AppDatabase {

companion object {
    fun init(context: Context) {
        Realm.init(context)

        val hasKey = "xxxxx-key_from_server-xxxxxx".getSHA512Pass()

        try {
            val config = RealmConfiguration.Builder()
                .assetFile("org.realm")
                .encryptionKey(hasKey.toByteArray())
                .schemaVersion(1)
                .readOnly()
                .build()

            Realm.setDefaultConfiguration(config)

        } catch (exception: Exception) {
            Timber.e(exception)
        }
    }
}}

It crash with this exception:

java.lang.IllegalArgumentException: The provided key must be 64 bytes. Yours was: 128

I tried implementing Base64,BigInteger(hasKey, 16).toByteArray(), and some other approaches but they didn't give me the required length. and I don't know if that will work.

Any suggestion will be appreciated.

Answer 1

Found the solution for the problem here: https://github.com/realm/realm-java/issues/2835

I just apply this to my Hex and gives me the require length:

public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
    data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                         + Character.digit(s.charAt(i+1), 16));
}
return data;

}