decoy.rs

`crates/veilvoice-crypto/src/decoy.rs`

veilvoice-crypto · 464 lines · read the source here · or on GitHub

A second passphrase that opens a different, empty VeilVoice.

What this is for, and what it is honestly worth

Somebody can be made to unlock a program. A decoy passphrase gives them something true to say: it opens VeilVoice, the application works, and there is nothing in it.

It does not give you deniability, and anyone who tells you otherwise is selling something. VeilVoice is open source. This file is published. An adversary who knows what they are looking at knows the feature exists, can read exactly how it works, and can simply ask for the other passphrase. What a decoy buys is a way to comply without revealing; what it does not buy is any argument that there is nothing more to reveal. SCOPE says that in the words a front end must show, and it is the most important thing this crate produces.

The destructive duress passphrase is deliberately not here

The roadmap asked for two things: a decoy, and a duress passphrase that destroys data. The second is not shipped, and WHY_NO_DESTRUCTION is the reason in full. In short: VeilVoice cannot promise a file is gone.

On flash storage a write does not overwrite. The controller maps a logical block to a new physical page and leaves the old one holding the data until it is garbage-collected, which may be minutes or may be never, and no program running as an ordinary user can reach it. This project already documents that about its own secure-erase feature and refuses to overstate it there.

A destructive duress passphrase would be believed in exactly the situation where being wrong costs the most. Somebody types it expecting the recordings to be gone; the ciphertext is still in unmapped pages; and they then behave as though it is not. A control people rely on and that does not work is worse than no control at all. So there is not one.

Typing the wrong one by mistake

The other failure the roadmap named, and the reason this shape was chosen. Because the decoy destroys nothing, typing it by accident costs a relaunch and nothing else. There is no state to recover and no decision that cannot be taken back. That is not a happy accident; it is why the destructive design was rejected rather than made safer.

Both passphrases are checked the same way

Which one matched must not be visible in how long the check took. Both are derived with the same Argon2id parameters and compared in constant time, and both are always derived even when the first one matches: returning early would make a real passphrase measurably faster than a decoy, which tells an observer with a stopwatch which of the two they just watched somebody type.

In plain words

You can set a second passphrase. Typing it opens VeilVoice normally, except that it is empty: no recordings, no projects, no history. It is there for the situation where somebody is standing over you asking you to unlock your computer.

Two honest warnings, and please read them.

It does not hide the fact that a second passphrase might exist. This program's source code is public and this feature is described in it, so anybody who recognises VeilVoice can ask you for the other one. It buys you a way to hand something over. It does not buy you an argument.

And there is no passphrase that destroys your recordings, deliberately. On modern storage, deleting a file does not reliably remove it, so a feature that claimed to would be lying to you at the worst possible moment.

WHAT THIS FILE CONTAINS

464 lines defining 9 functions (4 public), 4 types and 3 constants. Everything below is read out of the source, so it cannot disagree with the code.

The types it owns.

enum Opened line 76 · Which passphrase was given.
struct Pair line 90 · A pair of passphrase verifiers, checked together.
struct Verifier line 98 · One passphrase's stored form.
enum Refused line 141 · Why a pair was refused.

What happens when it runs. These are the ways in: public, and nothing else in this file calls them, so they are what an outside caller reaches first.

Pair::only_real line 198 · A real passphrase with no decoy.
reaches create
Pair::with_decoy line 214 · A real passphrase and a decoy.
reaches create, differences
Pair::has_decoy line 240 · Whether a decoy is set at all.
Pair::open line 251 · Which passphrase this is.

WHAT CALLS WHAT

The functions this file defines, and the calls between them. An edge means the callee's name appears, called, inside the caller's body. This is a syntactic reading, not a type-resolved one.

The same graph as Mermaid source

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flowchart TD
    n_create["Verifier::create<br/>line 104"]
    n_matches["Verifier::matches<br/>line 114"]
    n_constant_time_eq["constant_time_eq<br/>line 121"]
    n_fmt["Refused::fmt<br/>line 158"]
    n_differences["differences<br/>line 184"]
    n_only_real(["Pair::only_real<br/>line 198"])
    n_with_decoy(["Pair::with_decoy<br/>line 214"])
    n_has_decoy(["Pair::has_decoy<br/>line 240"])
    n_open(["Pair::open<br/>line 251"])
    n_matches --> n_constant_time_eq
    n_only_real --> n_create
    n_with_decoy --> n_create
    n_with_decoy --> n_differences
    click n_create href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L104" "open the source"
    click n_matches href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L114" "open the source"
    click n_constant_time_eq href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L121" "open the source"
    click n_fmt href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L158" "open the source"
    click n_differences href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L184" "open the source"
    click n_only_real href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L198" "open the source"
    click n_with_decoy href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L214" "open the source"
    click n_has_decoy href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L240" "open the source"
    click n_open href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-crypto/src/decoy.rs#L251" "open the source"
    classDef entry fill:#1f2335,stroke:#7aa2f7,color:#c0caf5
    class n_only_real,n_with_decoy,n_has_decoy,n_open entry
    classDef helper fill:#1f2335,stroke:#bb9af7,color:#c0caf5
    class n_create,n_matches,n_constant_time_eq,n_fmt,n_differences helper

This site loads no third-party script, so it cannot run Mermaid; the diagram above is the same nodes and edges drawn by the generator instead. GitHub renders the source below directly.

ITEMS

Item	Line	Documentation
`Opened` _{pub enum}	76	Which passphrase was given.
`Pair` _{pub struct}	90	A pair of passphrase verifiers, checked together.
`Verifier` _struct	98	One passphrase's stored form.
`Verifier::create` _fn	104
`Verifier::matches` _fn	114	Derive and compare.
`constant_time_eq` _fn	121	Compare without letting the time taken depend on where they differ.
`LEAST_DIFFERENCE` _{pub const}	137	How similar two passphrases may be before the pair is refused.
`Refused` _{pub enum}	141	Why a pair was refused.
`Refused::fmt` _fn	158
`differences` _fn	184	How many positions two passphrases differ in.
`Pair::only_real` _{pub fn}	198	A real passphrase with no decoy.
`Pair::with_decoy` _{pub fn}	214	A real passphrase and a decoy.
`Pair::has_decoy` _{pub fn}	240	Whether a decoy is set at all.
`Pair::open` _{pub fn}	251	Which passphrase this is.
`SCOPE` _{pub const}	275	What a decoy is worth, in the words a front end must show.
`WHY_NO_DESTRUCTION` _{pub const}	288	Why no passphrase destroys anything, and why that is the honest choice.