Week 12

Here is a brief summary of the progress last week.

I removed the google closure library from the extension last week and imported a new crypto library called forge, since forge is more compatible with openssl (we are using openssl for the publisher) and more developer-friendly in terms of API. Also, I added the function of signature verification to the client extension.

If the signature is verified with the publisher's public key, the content or what's signed under the signature is displayed.

If the signature is not verified, the extension prompts the user that the signature is not verified.

What's more, group key unwinding was implemented. We adopt the RSA scheme for group key winding and unwinding, which allows easy revocation and group state update. Basically, with the RSA private key (n, e, d), where n is the public modulus, e is the public exponent, and d is the private exponent, the group state m_i+1 = m_i^d mod n for winding or updating the group state, where m_i+1 is the updated group state, and m_i is the previous group state. Reversely, for unwinding the group state and retrieving the group key, m_i = m_i+1^e mod n, and the group key at state i is HASH(m_i).