Which versions of AeroVault are recommended and which are retired?

[EhudKirsh]

Which versions of AeroVault are legacy/retired/deprecated, and which are still recommended?

V4 is the latest, and V3 seems to be still actively recommended when Error Correction isn't used.

Is V3 = Chunking + Compression + V2? If so, then it's the other side of the coin of .aerozip, and still perfectly fine and should be recommended for a single file use whose only required wrapper is encryption.

Perhaps you might wish to take this opportunity to explain the difference between V1 and V2 and whether V1 should still have any use.

[axpnet]

Good question, and it is a fair one to ask because we have three different numbers floating around that are easy to conflate. Let me separate them first, then map the formats.

Three different "versions", do not mix them

What	Current value	Where it shows
AeroFTP app version	v4.0.7 (v4.0.8 next)	the desktop app, releases
aerovault crate version	0.6.2	the Rust library on crates.io that implements the formats
AeroVault on-disk format	a family, not a single number (see below)	inside the .aerovault file

So "v4" in the app sense (AeroFTP v4.0.x) is unrelated to the vault format, and the crate's 0.6.2 is unrelated to both. When you and we say "AeroVault V2 / V3 / V4" we mean the on-disk format family, which is what your question is really about.

The on-disk format families

Family	What it is	Compresses?	Dedup?	Error Correction	Status
Legacy encrypted ZIP	AES-256 over a ZIP (the original .aerovault)	yes (ZIP)	no	no	retired for new vaults, still opened
AEROVAULT2	AES-256-GCM-SIV container, Argon2id KDF, encrypted filenames	no	no	no	recommended default
AEROVAULT3	content-defined chunking, chunk dedup, zstd per chunk, AES-256-GCM-SIV	yes (zstd)	yes	optional	recommended for archives
AEROVAULT3 + Error Correction	the same AEROVAULT3 container with Reed-Solomon parity turned on	yes (zstd)	yes	yes	for corruption resilience

The security levels you see in the app map onto these:

• Standard / Advanced / Paranoid are all the AEROVAULT2 family (same container, increasing crypto: Advanced adds an HMAC-SHA512 header, Paranoid adds an AES + ChaCha20-Poly1305 cascade). Advanced is the recommended default.
• Archive is the AEROVAULT3 family.
• Error Correction is a toggle on AEROVAULT3, not a separate format.

So what has sometimes been called "V4" (or "rev 4") is AEROVAULT3 with Error Correction enabled, not a new container. An AEROVAULT3 reader without EC still opens it, because EC is a non-critical extension; it just does not use the parity.

Recommended vs retired (the direct answer)

• AEROVAULT2, Advanced level: recommended default for encrypting one file or a few files where the only wrapper you need is encryption. Fastest, encrypted filenames, strong AEAD.
• AEROVAULT3 (Archive): recommended when you want compression and/or deduplication, for larger or archival sets where dedup and zstd pay off.
• AEROVAULT3 + Error Correction: recommended when you want resilience to bit-rot / partial corruption, at the cost of storage overhead for the parity. If you do not need recoverable parity, plain AEROVAULT3 is the right choice, exactly as you said.
• Legacy ZIP: retired. Kept only so old .aerovault files keep opening. AEROVAULT2 supersedes it across the board (a real AEAD instead of ZIP encryption, encrypted filenames, no ZIP-decompression-bomb surface). Nothing new should be created as the ZIP format.

Your specific points

• "Is V3 = Chunking + Compression + V2?" Conceptually yes: AEROVAULT3 is AEROVAULT2-grade crypto (AES-256-GCM-SIV) plus content-defined chunking, deduplication and zstd compression. Implementation-wise it is its own container (AEROVAULT3 magic, different header) with per-chunk encryption, not AEROVAULT2 with a flag.
• One thing to watch in the internals: the AEROVAULT2 container carries an internal format-version byte whose current value happens to be 3 (it marks a hardened per-chunk AAD binding). That internal 3 is not "AeroVault format 3"; it shares the digit with AEROVAULT3 by coincidence. We track this trap in our format doc so nobody conflates the two.
• The "aerozip" compression lane, "the other side of the coin" Right framing. That lane (your own term, and the name is still being decided, see discussion #7) is compression-first with optional encryption, the 7z model, versus the .aerovault lane which is encryption-first. One nuance on the encrypted side: AEROVAULT2 does not compress (encryption only), so a single-file "encrypt only" case is AEROVAULT2 (Advanced), and a single-file "encrypt and compress" case is AEROVAULT3 (Archive).
• "V1 vs V2, should V1 still have a use?" AEROVAULT2 fully replaces the legacy ZIP. Keep the ZIP path only to read vaults you already made with it; create everything new as AEROVAULT2, or AEROVAULT3 / AEROVAULT3 + EC when you want the archive or error-correction features.

In short: Advanced (AEROVAULT2) for everyday encryption, Archive (AEROVAULT3) for compressed/deduplicated archives, Archive + Error Correction when you also want recoverable parity, and the legacy ZIP only for opening old vaults. And the app version (v4.0.x) and the aerovault crate version (0.6.2) are separate axes from the vault format, which is the main thing to keep straight.

[EhudKirsh]

If they aren't Versions, what does the V in V2, V3 and V4 stand for? Variants?

[axpnet]

Good question. The V does stand for "version", but specifically the on-disk format version: the third axis, separate from the app version (4.0.x) and the aerovault crate version (0.6.x). Not "variants".

It maps straight onto the families from above:

• V2 = the AEROVAULT2 family (its own magic bytes, 512-byte header).
• V3 = the AEROVAULT3 family: a different container with different magic bytes and a 1024-byte header. Each family's parser rejects the other's file before any decrypt, so V2 and V3 are genuinely separate formats, not interchangeable variants.
• V4 = the same AEROVAULT3 family with Error Correction added. It is not a new container or new magic, it is V3 plus a parity layer.

So "format generation" or "format level" is the most accurate reading: V2 and V3 are distinct on-disk families, and V4 is a capability level on top of V3. The full map is in docs/AEROVAULT-FORMATS.md.