secure-gate

Zero-cost, no_std-compatible wrappers for handling sensitive data in memory.

Fixed<T> – stack-allocated, zero-cost wrapper.
Dynamic<T> – heap-allocated wrapper with full .into() ergonomics.
When the zeroize feature is enabled, FixedZeroizing<T> and DynamicZeroizing<T> provide automatic zeroing on drop.

Now with conversions — the most requested ergonomics upgrade ever.

Installation

[dependencies]

secure-gate = "0.5.8"

Recommended (full power):

secure-gate = { version = "0.5.8", features = ["zeroize", "rand", "conversions"] }

Features

Feature	Description
`zeroize`	Automatic memory wiping on drop (via `zeroize` + `secrecy`) — recommended
`rand`	`SecureRandomExt::random()` — cryptographically secure key generation
`conversions`	NEW — `.to_hex()`, `.to_hex_upper()`, `.to_base64url()`, and `.ct_eq()` on all fixed secrets
`serde`	Optional serialization (deserialization disabled on `Dynamic<T>` for security)

Works in no_std + alloc. Only pay for what you use.

Quick Start

use secure_gate::{fixed_alias, dynamic_alias};

fixed_alias!(Aes256Key, 32);
fixed_alias!(FileKey, 32);
dynamic_alias!(Password, String);

// Cryptographically secure random keys
#[cfg(feature = "rand")]
{
    use secure_gate::SecureRandomExt;
    let key = Aes256Key::random();           // <80ns, thread-local OsRng
    let file_key = FileKey::random();
}

// Full ergonomics — with `conversions` feature
#[cfg(feature = "conversions")]
{
    use secure_gate::SecureConversionsExt;
    let hex = file_key.to_hex();             // "a1b2c3d4..."
    let b64 = file_key.to_base64url();       // safe for JSON, URLs
    assert!(file_key.ct_eq(&file_key));      // constant-time, timing-attack proof
}

// Heap secrets — pure joy
let pw: Password = "hunter2".into();
assert_eq!(pw.expose_secret(), "hunter2");

Secure Conversions — `conversions` feature

#[cfg(feature = "conversions")]
{
    use secure_gate::{fixed_alias, SecureConversionsExt, SecureRandomExt};

    fixed_alias!(FileKey, 32);
    let key = FileKey::random();

    println!("Key (hex):       {}", key.to_hex());
    println!("Key (Base64URL): {}", key.to_base64url());
    assert!(key.ct_eq(&key));  // required for secure comparison
}

.to_hex() / .to_hex_upper() → perfect for logging, debugging
.to_base64url() → ideal for JSON export, URLs, config files
.ct_eq() → mandatory for secure equality — prevents timing attacks

Memory Guarantees (`zeroize` enabled)

Type	Allocation	Auto-zero	Full wipe	Slack eliminated	Notes
`Fixed<T>`	Stack	Yes	Yes	Yes (no heap)	Zero-cost
`Dynamic<T>`	Heap	Yes	Yes	No (until drop)	Use `finish_mut()` to shrink
`FixedZeroizing<T>`	Stack	Yes	Yes	Yes	RAII wrapper
`DynamicZeroizing<T>`	Heap	Yes	Yes	No (until drop)	`SecretBox` prevents copies

Important: DynamicZeroizing<T> uses .expose_secret() — no Deref.

Macros

// Fixed-size secrets
secure!([u8; 32], rng.gen())                    // → Fixed<[u8; 32]>

// Heap secrets
secure!(String, "pw".into())                    // → Dynamic<String>
secure!(heap Vec<u8>, payload)                  // → Dynamic<Vec<u8>>

// Type aliases — the recommended way
fixed_alias!(Aes256Key, 32)
dynamic_alias!(Password, String)

Example Aliases

fixed_alias!(Aes256Key, 32);
fixed_alias!(XChaCha20Nonce, 24);
dynamic_alias!(Password, String);
dynamic_alias!(JwtSigningKey, Vec<u8>);

#[cfg(all(feature = "rand", feature = "conversions"))]
{
    use secure_gate::{SecureRandomExt, SecureConversionsExt};
    let key = Aes256Key::random();
    let hex = key.to_hex();          // only with `conversions`
    let pw: Password = "hunter2".into();
}

Zero-cost — proven on real hardware

Implementation	Median time	Overhead vs raw
raw `[u8; 32]`	~460 ps	—
`Fixed<[u8; 32]>`	~460 ps	**+28 ps
`fixed_alias!(Key, 32)`	~475 ps	+13 ps

Overhead is < 0.1 CPU cycles — indistinguishable from raw arrays.

View full report

Migration from v0.4.x

SecureGate<T> → Fixed<T> (stack) or Dynamic<T> (heap)
.expose_secret() → value.expose_secret()
Automatic zeroing → FixedZeroizing<T> or DynamicZeroizing<T>

Note: .view() and .view_mut() deprecated in v0.5.5 → removed in v0.6.0.

Changelog

CHANGELOG.md

License

MIT OR Apache-2.0

secure-gate 0.5.8