Defines actors, entry points, states, transitions, recovery paths, messages, and edge cases for SMS authentication. This reference fixes the adoption boundary, failure behavior, and observable evidence while leaving environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For SMS authentication, adopt a server-side credential and session lifecycle with explicit assurance. Define a deterministic user journey with visible state, reversible choices where possible, preserved input, and accessible recovery. This ux block focuses specifically on behavior and lifecycle. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The SMS authentication actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes required for the behavior and lifecycle focus of this ux block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Store only protected credential material, rotate signing and recovery secrets, and keep credentials out of URLs, logs, analytics, and support views.
- Bind issuance, use, expiry, revocation, recovery, and replay handling to a named subject and intended action.
- Return enumeration-resistant public responses while retaining sufficient internal reason and correlation data for support and abuse response.
- Re-evaluate sensitive actions after subject, device, authenticator, risk, or session state changes instead of trusting a stale login forever.
- Show progress only while work is actually pending and prevent duplicate activation without hiding the user's committed intent.
- Use plain, action-specific messages that distinguish validation, permission, connectivity, conflict, and terminal failure.
- Treat SMS as a possession signal with known interception and number-reassignment risk, not as phishing-resistant authentication.
- Rate-limit send and verify separately, use short single-purpose codes, hide enumeration, and offer safer recovery or step-up options.
- For the behavior and lifecycle variant, enforce this declared boundary: defines actors, entry points, states, transitions, recovery paths, messages, and edge cases for sms authentication.
Implementation guidance
- Prototype the longest, empty, slow, offline, denied, and assistive-technology paths before locking the happy-path layout.
- Model SMS authentication inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable SMS authentication contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- Missing, expired, replayed, or contradictory authentication evidence denies the action and follows a rate-bounded recovery path.
- Invalid or contradictory SMS authentication state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Complete the journey with keyboard, touch, screen reader, narrow viewport, delayed network, and a recoverable server error.
- Monitor SMS authentication success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.
References
- NIST SP 800-63B-4, Authentication and Authenticator Management (applies as of 2026-09-08)