Struct Nonce 

pub struct Nonce {
    pub value: String,
    pub created_at: i64,
}

A replay nonce used for ACME protocol anti-replay protection.

ACME Protocol Compliance

According to RFC 8555, nonces are used to prevent replay attacks:

• Each nonce is 32 random bytes from the system CSPRNG, base64url-encoded without padding — the octet-string form §6.5.1 requires, and 256 bits like every other non-guessable value in this tree
• Nonces are generated for every response
• Clients must include a valid nonce in their requests
• Nonces are single-use and expire after a TTL period

Security Considerations

• Nonces are stored in the database with timestamps
• Expired nonces are automatically cleaned up
• Single-use enforcement prevents replay attacks
• Time-to-live limits prevent indefinite nonce accumulation

Database Storage

Nonces are stored in the nonces table with:

• value: The base64url nonce string
• created_at: Unix timestamp when the nonce was created

Lifecycle

1. New nonce created for each response
2. Nonce saved to database
3. Client uses nonce in subsequent request
4. Nonce verified and consumed (single-use)
5. Expired nonces automatically cleaned up

Fields

value: String

created_at: i64

Implementations

impl Nonce

pub fn new() -> Self

pub async fn save(&self, database: &Database) -> Result<(), Error>

pub async fn verify( nonce: &str, database: &Database, ttl: Duration, ) -> Result<bool, Error>

Consumes nonce if it is live: a single DELETE whose rows_affected decides, so two concurrent replays cannot both succeed.

Takes &str rather than String — it only ever binds a reference, and this runs on every signed POST, which is the hottest path in the server.

pub async fn count(database: &Database) -> Result<i64, Error>

How many nonce rows exist right now.

The one thing worth showing about this table: individual values are bearer credentials and are never listed (see the note on fingerprint), but the count is a useful health signal — it should hover around the request rate times the TTL, and a number far above that means the reaper is not running.

pub async fn cleanup(database: &Database, ttl: Duration) -> Result<u64, Error>

Trait Implementations

impl Debug for Nonce

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Nonce

fn default() -> Self

Returns the “default value” for a type.