Somehow I never end up with a valid RSA-key in step 4.

my step 3 is:
private static SecretKeySpec passwordToSymmetricKey(final char[] password, byte[] salt) throws Exception {
// http://stackoverflow.com/questions/992019/java-256bit-aes-encryption
SecretKeyFactory f = SecretKeyFactory.getInstance(“PBKDF2WithHmacSHA1″);
KeySpec ks = new PBEKeySpec(password, salt, 1024, 128);
SecretKey s = f.generateSecret(ks);
SecretKeySpec k = new SecretKeySpec(s.getEncoded(), “AES”);

return k;
}

my step 4 is:
SecretKeySpec symmetricKey = passwordToSymmetricKey(passphrase.toCharArray(), salt);
Cipher cipher = Cipher.getInstance(“AES/CBC/NoPadding”);
IvParameterSpec ips = new IvParameterSpec(iv);
cipher.init(Cipher.UNWRAP_MODE, symmetricKey, ips);
Key decryptedPrivKey = cipher.unwrap(privKey, “RSA”, Cipher.PRIVATE_KEY);

the problem:
“invalid key format” (trying to parse the key as PKCS8=ASN.1)

@Gerv: We’re definitely thinking about deriving the password from the passphrase. thunder has been working on a spec: it’s available at https://wiki.mozilla.org/Labs/Weave/WEP/100 (Comments welcome!)