@eapl.me@eapl.me Here is what I’ve got so far: https://github.com/upputter/testing-twtxt-dm

There is a “00_well_known_message.enc” file, which I have the encryption paremters for (https://github.com/upputter/testing-twtxt-dm/blob/9fdf3be6aa8fe810a4cb275375dbb3d4a2a958ee/wellknown_test.php#L28).

According to my finding, I assume, that the saltsize in openssl is “8” and the PBKDF2 algo is “sha256”.

@arne@uplegger.eu Here are the results of the german jury:

Known salt (B64): Tb9oj07UhwU= (8)
Known key (B64): MII0yj+MC0mHNx254Voar80bi9P7jmocs0+x+inaxBE=
Known iv (B64): l/PvkDjOKMFZe73KptrvWw== (16)
Shared Key (B64): ql8zvN03p6kroSwNrcKbxk4zSBQFkgQZEumvqVIDMAE=
** DECRYPT **
Encrypted Message: ...
Decoded Salt (B64): Tb9oj07UhwU= (8)
PBKDF2 KEY (B64): MII0yj+MC0mHNx254Voar80bi9P7jmocs0+x+inaxBE=
iv (B64): JanbU1jI30lb6yfjq/adjA== (16)
Decrypted Message: 

😭

here is my progress so far: https://github.com/eapl-gemugami/twtxt-direct-message-php
The encryption part seems to work, if I decrypt it the message with OpenSSL.
I think it can help you for some key parts not well explained in OpenSSL documentation.

@andros@twtxt.andros.dev reading your spec I wrote a few notes here: https://github.com/eapl-gemugami/twtxt-direct-message-php/blob/main/direct_message_spec.md

@arne@uplegger.eu I haven’t check your repo yet, although you are using sodium, right?

@eapl_en@eapl.me Your notes are amazing! I’m going to save them for when I do my implementation. Great job!