Google play app signing key hash

The easiest way would be to copy Facebook's error message and copy the keyhash they were expecting to get from there.

Just make sure you are using your Google Play downloaded app :)

You can extract keyhash from the Sha1 certificate signature. Key hashes are usually extracted in the following way:

public static String getKeyHash(final Context context) {
    PackageInfo packageInfo = getPackageInfo(context, PackageManager.GET_SIGNATURES);
    if (packageInfo == null)
        return null;

    for (Signature signature : packageInfo.signatures) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA");
            md.update(signature.toByteArray());
            return Base64.encodeToString(md.digest(), Base64.NO_WRAP);
        } catch (NoSuchAlgorithmException e) {
            Log.w(TAG, "Unable to get MessageDigest. signature=" + signature, e);
        }
    }
    return null;
}

You can see that SHA-1 version of signature is Base64 encoded.

Under App Signing menu in Google play developer console, you will see Sha-1 certificate signature that looks like this:

SHA1: 3B:DA:A0:5B:4F:35:71:02:4E:27:22:B9:AC:B2:77:2F:9D:A9:9B:D9

Basically, what you have to do is to change this into a byte array and Base64 encode that byte array. You can do something like:

byte[] sha1 = {
    0x3B, (byte)0xDA, (byte)0xA0, 0x5B, 0x4F, 0x35, 0x71, 0x02, 0x4E, 0x27, 0x22, (byte)0xB9, (byte)0xAc, (byte)0xB2, 0x77, 0x2F, (byte)0x9D, (byte)0xA9, (byte)0x9B, (byte)0xD9
};
Log.e("keyhash", Base64.encodeToString(sha1, Base64.NO_WRAP));

You can register this keyhash to facebook android login settings or wherever you like.

You can convert SHA-1 hash in hex format (as found in Play console, see Release management -> App Signing) into base64 hash using next command:

echo 33:4E:48:84:19:50:3A:1F:63:A6:0F:F6:A1:C2:31:E5:01:38:55:2E | xxd -r -p | openssl base64

Output:

M05IhBlQOh9jpg/2ocIx5QE4VS4=

This hash can be used for example when setting up Facebook app.