Start an SCA login

Begin an SCA login for the customer with the chosen factor, opening the end-user SCA session (an exemption gating read / account access beyond the per-transaction window). Returns factor-specific material: SMS_OTP dispatches a code and returns a challengeId + expiresAt; TOTP returns only the factor (the customer reads the code from their app); PASSKEY returns WebAuthn passkeyOptions. Complete with POST /sca/login/complete.

This endpoint is only meaningful for customers in a region where SCA is required (e.g. EU). For customers outside SCA-regulated regions, this returns 409.

POST /sca/login/start

Start an SCA login

cURL

curl --request POST \
  --url https://api.lightspark.com/grid/2025-10-13/sca/login/start \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '{}'

200

{
  "factor": "SMS_OTP",
  "challengeId": "<string>",
  "expiresAt": "2025-10-03T12:05:00Z",
  "passkeyOptions": {},
  "allowedOrigins": [
    "https://app.example.com"
  ],
  "relyingPartyId": "app.example.com"
}

Authorizations

Authorization · string · header · required

API token authentication using format <api token id>:<api client secret>

Query Parameters

customerId · string · required

The unique identifier of the customer starting an SCA login.

Body

application/json

Selects which enrolled factor to start an SCA login with. The factor must already be enrolled (or, for SMS_OTP, the phone verified).

factor · enum<string> · required

The factor to authenticate with.

Available options: SMS_OTP, TOTP, PASSKEY

Response

200

application/json

SCA login started; factor-specific material is returned.

The factor-specific material a customer needs to complete an SCA login. Each factor surfaces only the fields it issues: SMS_OTP carries challengeId and expiresAt; TOTP carries neither (the customer reads the code from their authenticator app); PASSKEY carries the opaque WebAuthn passkeyOptions with allowedOrigins and relyingPartyId.

factor · enum<string> · required

The factor this login was started for.

Available options: SMS_OTP, TOTP, PASSKEY

challengeId · string | null

The challenge handle for an SMS_OTP login, threaded back on the complete call. Present only for SMS_OTP.

expiresAt · string<date-time> | null

Absolute UTC timestamp after which the SMS_OTP code expires. Present only for SMS_OTP.

Example:

"2025-10-03T12:05:00Z"

passkeyOptions · object | null

Opaque WebAuthn assertion request options. Present only for PASSKEY; pass to the device's WebAuthn API to produce the assertion submitted on the complete call.

allowedOrigins · string[] | null

The origins the WebAuthn ceremony may run against. Present only for PASSKEY.

Example:

["https://app.example.com"]

relyingPartyId · string | null

The WebAuthn relying-party id. Present only for PASSKEY.

Example:

"app.example.com"