age_writer.dart ports age.Encrypt of filippo.io/age v1.3.2, with its
checks and texts. AgeEncryptor and ageEncrypt draw the file key, wrap it
for each recipient in its order, with its labels, compute the header MAC
and draw the nonce: no recipients, labels that cannot be mixed, a
recipient that fails and stanzas that cannot be marshalled give Go's
errors. AgePayloadEncryptor encrypts the STREAM as its plaintext
arrives, as Go's EncryptWriter: a full chunk waits for the next byte,
so the last one is full-length for a non-zero multiple of 64 KiB and
empty only for an empty plaintext. The lengths of a file follow from its
plaintext and the form of its stanzas, before anything is encrypted.
recipient.dart has X25519Recipient, with its age1 strings and the texts
of ParseX25519Recipient; ScryptRecipient, with its random label;
TimeRecipient, with the label datekeys-tlock- of agewrap;
checkX25519Recipient, with the texts of agewrap.CheckX25519Recipient;
generateX25519Identity and the raw keys of agewrap.
The tests write every file of age_writer.json again with the same seed,
whole and in pieces, and get the same draws and bytes; open each with
the readers of this library; and check the errors, the recipients, the
STREAM and the lengths, on the VM and, without the expensive cases, on
Node.js.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
