Hi everyone,
I'm new to the list and thank you for approving my account to join such a
diverse group!
I'm a Wickr co-founder and I heard there was some discussion today about our
technology. As you've probably heard Dan Kaminsky is part of our advisory
board and we've worked out some additional details about our technology that
we'd like to share with you. I hope you'll appreciate what we've been working
so hard on.
Below is what we've come up with attached with greetings from Dan.
Hi everyone, this is Dan Kaminsky. I've been advising Wickr for some time, and
I'm relatively pleased with the nature of the product we're offering here..
Essentially, it's an attempt to create an environment where the best practices
of secure messaging are "always on" and "just work". There are quite a few
communities that we all agree could use an easier way to communicate safely,
and we're honored to provide this new service. A couple of comments about how
it all works:
Obviously, there's no home grown crypto. It's 2012, everyone knows how that
story ends. Messages are encrypted via multiple rounds of AES-256, with the
symmetric keys transported via 4096 bit RSA. Private keys actually never leave
the decrypting device; in fact, Wickr goes out of its way to bind messages to a
particular device as thoroughly as feasible. It actually uses some properties
of devices that are unique from phone to phone as part of the key material
necessary to decrypt messages to a particular phone. We sacrifice some
usability to achieve device dependence but feel the paranoia is justified.
There is indeed a central server in the Wickr design; it's there to introduce
peers to one another and to provide some protection against traffic analysis
while proxying messages between peers. Critically, the Wickr server never sees
the plaintext and does not have a backup of the private keys. Encrypted
messages are delivered to the central server via SSL and a Wickr-specific key,
and then they are proxied to clients for decryption and display.
The central server really does as much as it can to proxy content, but
otherwise gets out of the way. No logs are kept of message delivery, all
addresses are SHA-256 hashes of keys, and each device stores a unique
cryptographic hash for each Wickr peer.
Regarding forward secrecy, as a store and forward platform there are some
challenges. Wickr's model is to use the server side key to rotate the client
side key on a regular basis, at periods longer than the maximum supported
expiration time. This is vaguely similar to the key rotation strategy used by
OpenSSH. It's not PFS but it's quite reasonable.
Anyway, Wickr is under active development, so please, kick the tires! Let us
know what you think!
Thanks again everyone for the opportunity to post.
~Kara
k...@mywickr.com
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