There is a lot more information on this on her fantastically well written blog:

We have chosen to use elliptic curve cryptography and specifically, we've chosen to use (all hail the NSA?

) P256, for use with Elliptic curve Diffie–Hellman (ECDH) as our ephemeral key agreement protocol, Elliptic Curve Digital Signature Algorithm (ECDSA) over P256 as our digital signature algorithm (512 bits in length giving 128 bits of security), SHA-512 as our hash function (512 bits in length), HMAC as our MAC over our hash function (128 bits in length), AES-128 in CTR with a random IV for encryption (128 bits of key material, obviously), BASE64 for encoding of data, keys and HTTP for the transport - we assume HTTPS or Tor Hidden Service and consider those details out of scope.

If you want some more info or want to see the pictures of the livers (some people might be interested! ) you should check out Polly's (Hugo's mummy) blog: https://lifeofalivermum.wordpress.com/2015/06/10/third-time-lucky/ Thank you all for your kind donations! xxx Hey guys, we would all like to thank you all for your kind donations and generosity. My amazing big brother Ross (Hugo's daddy) is a match and we are just waiting for a date for the op!

It really shows how kind and sweet people can truly be. I don't think I have ever felt more proud of anyone.

Each chat message is encrypted with AES in CTR mode with the group session key and signed with the sender's ephemeral ECDSA key.

Alice, Bob, Mallory, and Eve wish to have a chat using the XMPP chat server in the channel '#protocol-spec'.

Currently, each party generates a 128-bit random value, and exchanges it pairwise with all other participants using Elliptic Curve Diffie-Hellman authenticated by each principal's ephemeral private key.

The group session key is then the hash of all principals' random values, arranged lexicographically.

Our implementation is mostly a toy but we believe it is a reasonable first stab at creating a simple mp OTR demonstration.

With native implementations, we believe that mp OTR is a very reasonable encrypted chat protocol but our implementation is by no means peer-reviewed and should be considered an experiment.

On September 29th 2014 their world became complete when Polly gave birth to my wonderful little nephew Hugo.