Predicates

The three predicate methods on OctetSdk.loc. All three are async (Swift) / suspend (Kotlin) and do not throw. Runtime problems surface as INDETERMINATE verdicts, not exceptions.

isWithin

The primary predicate. Reads as: "my currently provable location is inside region."

public func isWithin(
    region: OctetRegion,
    atTime: Date = Date(),
    sessionNonce: Data? = nil,
    decisionRef: String? = nil,
    forceFresh: Bool = false
) async -> OctetVerdict

suspend fun isWithin(
    region: OctetRegion,
    atTime: Instant = Instant.now(),
    sessionNonce: ByteArray? = null,
    decisionRef: String? = null,
    forceFresh: Boolean = false,
): OctetVerdict

Example

let v = await sdk.loc.isWithin(
    region: .country(isoCode: "US"),
    atTime: Date()
)
if v.result == .yes { ship(v.proof!) }

val v = sdk.loc.isWithin(
    region = OctetRegion.country("US"),
    atTime = Instant.now()
)
if (v.result == OctetVerdict.Result.YES) ship(v.proof!!)

isOutside

Reads as: "my currently provable location is outside region."

public func isOutside(
    region: OctetRegion,
    atTime: Date = Date(),
    sessionNonce: Data? = nil,
    decisionRef: String? = nil,
    forceFresh: Bool = false
) async -> OctetVerdict

suspend fun isOutside(
    region: OctetRegion,
    atTime: Instant = Instant.now(),
    sessionNonce: ByteArray? = null,
    decisionRef: String? = null,
    forceFresh: Boolean = false,
): OctetVerdict

contains

Reads from the device's perspective: "my location contains this point within tol meters."

public func contains(
    center: LatLon,
    tol: Meters,
    atTime: Date = Date(),
    sessionNonce: Data? = nil,
    decisionRef: String? = nil,
    forceFresh: Bool = false
) async -> OctetVerdict

suspend fun contains(
    center: LatLon,
    tol: Meters,
    atTime: Instant = Instant.now(),
    sessionNonce: ByteArray? = null,
    decisionRef: String? = null,
    forceFresh: Boolean = false,
): OctetVerdict

Mathematically equivalent to isWithin(region: .disc(center: center, radiusMeters: tol), atTime:). Kept as a distinct verb because the device-centric reading is the natural one for proximity use cases ("am I near the delivery dropoff", "did I arrive at the geofence").

Rolling your own

isWithin is the load-bearing primitive. contains is a thin one-liner over it. The same trick rolls custom predicates:

extension OctetLoc {
    func isNear(_ center: LatLon, _ tol: Meters) async -> OctetVerdict {
        await isWithin(region: .disc(center: center, radiusMeters: tol))
    }
    func isInsideAny(_ regions: [OctetRegion]) async -> OctetVerdict? {
        for r in regions {
            let v = await isWithin(region: r)
            if v.result == .yes { return v }
        }
        return nil
    }
}

suspend fun OctetLoc.isNear(center: LatLon, tol: Meters): OctetVerdict =
    isWithin(OctetRegion.disc(center, tol))

suspend fun OctetLoc.isInsideAny(regions: List<OctetRegion>): OctetVerdict? {
    for (r in regions) {
        val v = isWithin(r)
        if (v.result == OctetVerdict.Result.YES) return v
    }
    return null
}

Time semantics

All three predicates take an optional atTime. See Time Semantics for the live / historical / future regimes and the per-resolution validity windows. Default is "now". Future times beyond ±2 s come back INDETERMINATE / FUTURE_TIME.

Proof binding and freshness

All three predicates take three optional controls over which proof answers the call:

• sessionNonce (opaque bytes, 1 to 512) binds the proof to one login. The SDK commits a hash of the nonce inside the signed proof, so a verifier can confirm the proof was made for that login. An empty or over-512-byte nonce returns INDETERMINATE / INVALID_SESSION_NONCE.
• decisionRef (1 to 256 characters) binds the uploaded proof to one authorization decision, tagging the upload envelope with decision_ref and region_ref. An over-256-character ref returns INDETERMINATE / INVALID_DECISION_REF, with no network call.
• forceFresh bypasses the freshness buffer and mints a proof for this call, with none of the binding semantics above.

Each of sessionNonce and decisionRef forces a fresh proof. Setting forceFresh as well is redundant but harmless.

let nonce = try await loginBackend.issueNonce()
let v = await sdk.loc.isWithin(region: .country(isoCode: "US"), sessionNonce: nonce)
if v.result == .yes { send(v.proof!, to: loginBackend) }

Proof Binding explains when to use each, and how a bound proof is verified.

See also

• OctetRegion. The shapes you can pass.
• OctetVerdict. What you get back.
• Proof Binding. Binding a proof to a login or a decision.
• Verdicts. The trichotomy and the ReasonCode taxonomy.