opmsg is a replacement for gpg which can encrypt/sign/verify your mails or
create/verify detached signatures of local files. Even though the opmsg
output looks similar, the concept is entirely different.

* Perfect Forward Secrecy (PFS) by means of ECDH or DH Kex.
* Native EC or RSA fallback if no (EC)DH keys left.
* Signing messages is mandatory.
* OTR-like deniable signatures if demanded.
* Support for 1:1 key bindings to auto-select source key per
destination.
* Adds the possibility to (re-)route messages different from mail
address to defeat meta data collection.
* Key format suitable for easy use with QR codes.
* Optional cross-domain ECDH Kex.