Chat encryption: what it was, where it went
From 1.19.2-v1.13.0 to v2.11.0 the mod could encrypt your chat with a shared secret key. It was removed in 1.21.5-v2.12.0 — unmaintained and buggy, and dedicated mods now do the job better.
The idea was simple: pick an algorithm (AES by default), generate a key or derive
one from a passphrase, share it with the people you trust, and your messages travel as
ciphertext. To everyone without the key — including the server console — a
message looked like gwZnkzO5aBmUcY0BpIz/ApCNNkzp7g==. To your friends
with the key, plain text with a lock icon. Reporting gibberish accomplishes nothing,
which was the point.
You configured it by right-clicking the padlock button in the chat screen, and it
could encrypt public chat or just command channels like /msg, with keys
shared out-of-band. Aizistral's
video walks through the whole thing, including whether it was worth using at all.
Where that leaves you today: builds through 1.21.4 still ship the feature, and the maintained 1.20.1 line is the comfortable way to have it. On current versions, the wiki's alternatives list points to dedicated tools — SecureChat for encrypted text on modern Fabric, Simple Voice Chat and Plasmo Voice for AES-encrypted voice, Message Encryption for private messages, or simply moving sensitive talk to Discord, where Minecraft's report system can't follow. The full list with versions lives in the wiki's alternatives section.
Condensed from the official wiki's To Encrypt or Not to Encrypt article, which stays the canonical reference.
The maintained line that still ships encryption.