Enum PresenceMode 

pub enum PresenceMode {
    Cached,
    Strict,
    None,
}

User-presence prompt cadence for sign operations.

Orthogonal to AccessPolicy: AccessPolicy says what counts as authentication (e.g. fingerprint vs. passcode); PresenceMode says how often the user must reproduce it.

On macOS the choice is implemented by passing (or omitting) a long-lived LAContext to CryptoKit’s SecureEnclave.P256.Signing.PrivateKey.

Other platforms do not have an analogous cached-context concept and treat all variants identically:

• Windows TPM (CNG): The hardware enforces NCRYPT_UI_POLICY per sign, so every signature triggers a fresh Windows Hello prompt.
• Linux TPM and software / keyring backends: No gate at all. AccessPolicy is stored in metadata but is not consulted at sign or decrypt time, so all PresenceMode variants behave the same as PresenceMode::None. See the “Linux TPM backend” section of THREAT_MODEL.md.

Variants

Cached

User-presence prompt batched within a TTL window. The first sign after the cache is cold prompts; subsequent signs within the cache TTL reuse the same LAContext and are silent. This is the default for any new key created with user-presence enabled.

Strict

User-presence prompt on every sign. The agent does not pass a long-lived LAContext, so the SEP enforces a fresh authentication per signature.

None

No user-presence prompt. The key has AccessPolicy::None (or its platform equivalent) and signs silently regardless of cache state.

Implementations

impl PresenceMode

pub fn migration_default(policy: AccessPolicy) -> Self

Migration default for keys whose .meta predates presence_mode: historically, a key with any access policy other than None effectively had Strict semantics (one prompt per sign), and a key with None was silent. Use this when reading a legacy .meta file with no presence_mode field.

Trait Implementations

impl Clone for PresenceMode

fn clone(&self) -> PresenceMode

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for PresenceMode

impl Debug for PresenceMode

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

Formats the value using the given formatter.

impl Default for PresenceMode

fn default() -> PresenceMode

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for PresenceMode

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for PresenceMode

impl PartialEq for PresenceMode

fn eq(&self, other: &PresenceMode) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for PresenceMode

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for PresenceMode