covert 0.3.2

File and message encryption program

Covert Encryption

A file and message encryptor with strong anonymity

• ChaCha20-Poly1305 stream cipher with authentication
• Argon2 secures shorter passwords against cracking
• Curve25519 public key encrypt & sign with SSH, Age and MiniSign keys

Anonymity, privacy and authenticity

The encrypted archive looks exactly like random data, providing deniability. Every byte is protected so that not only is reading prevented but authenticity is also verified, protecting your data against any outsiders, and files may also be signed if necessary.

Other encryption tools add unencrypted headers revealing the recipients and other metadata. Covert was created to address this very problem, to stop all information leakage.

A message (base64 or binary) has no headers or anything else that could be recognized:

HDGKMFEo5cYHtUF1w9aNlX1lMmWJD3B7p8HoBoQZTNJGjg/nUOMqlXLspmmVO7PQj8Pe

Covert generates easy passphrases like pinkmuletibetdemand for the above. The encoded message includes random padding to hide the length of the message and it is still shorter than others.

For comparison, gpg needs six lines instead of one and still ends up revealing the exact length of the message. It also claims that this passphrase is insecure while happily accepting very common passwords like passw0rd and password1 (that are correctly rejected by Covert). Please, do not require digits or symbols in passphrases, it only weakens your security!

Try it!

Python pip will add covert on your system. Decrypt the above message to see what it says:

pip install covert
covert dec

File I/O speeds matching the fastest SSDs

Covert is the fastest of all the popular tools in both encryption (blue) and decryption (red).

Program	Lang	Algorithms	Operation
Covert	Python	chacha20‑poly1305 sha512‑ed25519	encrypt with auth and signature
Age	Go	chacha20-poly1305	encrypt with auth
Rage	Rust	chacha20-poly1305	encrypt with auth
OpenSSL	C	aes256-ctr (hw accelerated)	encrypt only
GPG	C	aes128-cfb, deflate	encrypt with auth and compression
MiniSign	C	blake2b-512 ed25519	signature only (for reference)

A few interesting features

Files of any size may be attached to messages without the use of external tools, and without revealing any metadata such as modification times.

A completely different ciphertext is produced each time, usually of different size, even if the message and the key are exactly the same. Other crypto tools cannot do this.

Covert messages are much shorter than with other cryptosystems, accomplished by some ingenious engineering.

A key insight is that a receiver can blindly attempt to decrypt a file with many different keys and parameters until he finds a combination that authenticates successfully. This saves valuable space on short messages and improves security because no plain text headers are needed.

Additional reading

• Covert Format Specification
• Covert Encryption Security
• Reducing Metadata Leakage (a related research paper)
• The PGP Problem

Covert is in an early development phase, so you are encouraged to try it but avoid using it on any valuable data just yet. We are looking for interested developers and the specification itself is still open to changes, no compatibility guarantees.