Paper version 2

[maxtaco]

• Local Key Security
• add join/leave protocol security properties
• remove an unintentional \mathit
• rename meeting security code to meeting leader security code
• add deep fake definition
• Replace Dual* Public Key operations with simple calls to libsodium
  • We've determined that we don't need to double up on all public key crypto ops, so we just redefined all of our primitives in terms of libsodium specifics.
• some small cleanups
  • use ref not namref
  • reorder some sections
  • attached -> detached signatures
  • changelog updates
  • readme updates
  • paper location updates
  • add Julia Len author