Implement email verification with the Digital Credentials API

This guide describes how to implement verified email retrieval using the Digital Credentials Verifier API through an OpenID for Verifiable Presentations (OpenID4VP) request.

Add dependencies

In your app's build.gradle file, add the following dependencies for Credential Manager:

Kotlin

dependencies {
    implementation("androidx.credentials:credentials:1.7.0-alpha01")
    implementation("androidx.credentials:credentials-play-services-auth:1.7.0-alpha01")
}

Groovy

dependencies {
    implementation "androidx.credentials:credentials:1.7.0-alpha01"
    implementation "androidx.credentials:credentials-play-services-auth:1.7.0-alpha01"
}

Initialize Credential Manager

Use your app or activity context to create a CredentialManager object.

// Use your app or activity context to instantiate a client instance of
// CredentialManager.
private val credentialManager = CredentialManager.create(context)

Construct the Digital Credential request

To request a verified email, construct a GetCredentialRequest containing a GetDigitalCredentialOption. This option requires a requestJson string formatted as an OpenID for Verifiable Presentations (OpenID4VP) request.

The OpenID4VP request JSON must follow a specific structure. The current providers support a JSON structure with an outer "digital": {"requests": [...]} wrapper.

        val nonce = generateSecureRandomNonce()

// This request follows the OpenID4VP spec
        val openId4vpRequest = """
    {
      "requests": [
        {
          "protocol": "openid4vp-v1-unsigned",
          "data": {
            "response_type": "vp_token",
            "response_mode": "dc_api",
            "nonce": "$nonce",
            "dcql_query": {
              "credentials": [
                {
                  "id": "user_info_query",
                  "format": "dc+sd-jwt",
                   "meta": { 
                      "vct_values": ["UserInfoCredential"] 
                   },
                  "claims": [ 
                    {"path": ["email"]}, 
                    {"path": ["name"]},  
                    {"path": ["given_name"]},
                    {"path": ["family_name"]},
                    {"path": ["picture"]},
                    {"path": ["hd"]},
                    {"path": ["email_verified"]}
                  ]
                }
              ]
            }
          }
        }
      ]
    }
    """

        val getDigitalCredentialOption = GetDigitalCredentialOption(requestJson = openId4vpRequest)
        val request = GetCredentialRequest(listOf(getDigitalCredentialOption))

The request contains the following key information:

DCQL query: The dcql_query specifies the credential type and the claims being requested (email_verified). You can request other claims to determine the level of verification. A few possible claims are as follows:
- email_verified: In the response, this is a Boolean that indicates whether the email is verified.
- hd (hosted domain): In the response, this is empty.
Note: If email_verified is true and hd is empty in the response, it implies that the account is an authorized Google Account. Currently, Google does not issue verifiable credentials for Google Workspace Accounts. However, the hd field is present in verifiable credentials issued for non-workspace accounts. You are encouraged to implement handling this field to future-proof your app.
If the email is non-@gmail.com, Google verified this email when the Google Account was created, but there is no freshness claim. Therefore, for non-Google emails, you should consider an additional challenge, such as an OTP, to verify the user. To understand the schema of the credential and the specific rules for validating fields like email_verified, refer to the Google Identity guides.
nonce: A unique, cryptographically secure random value is generated for each request. This is critical for security, as it prevents replay attacks.
UserInfoCredential: This value implies a specific type of digital credential that contains user attributes. Including this in the request is pivotal to distinguish the email verification use case.

Next, wrap the openId4vpRequest JSON in a GetDigitalCredentialOption, create a GetCredentialRequest, and call getCredential().

Present the request to the user

Present the user with the request, using the Credential Manager built-in UI.

try {
    // Requesting Digital Credential from user...
    val result = credentialManager.getCredential(activity, request)

    when (val credential = result.credential) {
        is DigitalCredential -> {
            val responseJsonString = credential.credentialJson

            // Successfully received digital credential response.

            // Next, parse this response and send it to your server.
            // ...
        }

        else -> {
            // handle Unexpected State() - Up to the developer
        }
    }
} catch (e: Exception) {
    // handle exceptions - Up to the developer
}

Parse the response on the client

After receiving the response, you can perform a preliminary parse on the client. This is useful for immediately updating the UI, for example, by showing the user's name.

The following code extracts the raw Selective Disclosure JWT (SD-JWT) and uses a helper to decode its claims.

// 1. Parse the outer JSON wrapper to get the `vp_token`
val responseData = JSONObject(responseJsonString)
val vpToken = responseData.getJSONObject("vp_token")

// 2. Extract the raw SD-JWT string
val credentialId = vpToken.keys().next()
val rawSdJwt = vpToken.getJSONArray(credentialId).getString(0)

// 3. Use your parser to get the verified claims
// Server-side validation/parsing is highly recommended.

// Assumes a local parser like the one in our SdJwtParser.kt sample
val claims = SdJwtParser.parse(rawSdJwt)
Log.d("TAG", "Parsed Claims: ${claims.toString(2)}")

// 4. Create your VerifiedUserInfo object with REAL data
val userInfo = VerifiedUserInfo(
    email = claims.getString("email"),
    displayName = claims.optString("name", claims.getString("email"))
)

Handle the response

The Credential Manager API will return a DigitalCredential response.

The following is an example of what the raw responseJsonString looks like, and what the claims look like after parsing the inner SD-JWT where you get additional metadata as well along with verified email:

/*
// Example of the raw JSON response from credential.credentialJson:
{
  "vp_token": {
    // This key matches the 'id' you set in your dcql_query
    "user_info_query": [
      // The SD-JWT string (Issuer JWT ~ Disclosures ~ Key Binding JWT)
      "eyJhbGciOiJ...~WyI...IiwgImVtYWlsIiwgInVzZXJAZXhhbXBsZS5jb20iXQ~...~eyJhbGciOiJ..."
    ]
  }
}

// Example of the parsed and verified claims from the SD-JWT on your server:
{
  "cnf": {
    "jwk": {..}
  },
  "exp": 1775688222,
  "iat": 1775083422,
  "iss": "https://verifiablecredentials-pa.googleapis.com",
  "vct": "UserInfoCredential",
  "email": "jane.doe.246745@gmail.com",
  "email_verified": true,
  "given_name": "Jane",
  "family_name": "Doe",
  "name": "Jane Doe",
  "picture": "http://example.com/janedoe/me.jpg",
  "hd": ""
}
 */

Server-side validation for account creation

Since the retrieved email is cryptographically verified, you can omit the email OTP verification step, significantly reducing sign-up friction and potentially increasing conversion. This process is best handled on your server. The client sends the raw response (containing the vp_token) and the original nonce to a new server endpoint.

For verification, your application must send the full responseJsonString to your server for cryptographic validation before creating an account or logging the user in.

The digital credential provides two critical levels of verification for your server:

Authenticity of the data: Verifying the issuer (iss) URL and the SD-JWT signature proves that a trusted authority issued this data.
Identity of the presenter: Verifying the cnf field and the Key Binding (kb) signature confirms that the credential is being shared by the same device it was originally issued to, preventing it from being intercepted or used on another device.

The validation on the server must achieve the following:

Verify issuer: Ensure the iss (issuer) field matches https://verifiablecredentials-pa.googleapis.com.
Verify signature: Check the signature of the SD-JWT using the public keys (JWKs) available at https://verifiablecredentials-pa.googleapis.com/.well-known/vc-public-jwks.

For full security, make sure that you also validate the nonce to prevent replay attacks.

By combining these steps, your server can validate both the authenticity of the data and the identity of the presenter, ensuring the credential wasn't intercepted or spoofed before provisioning the new account.

try {
    // Send the raw credential response and the original nonce to your server.
    // Your server must validate the response. createAccountWithVerifiedCredentials
    // is a custom implementation per each RP for server side verification and account creation.
    val serverResponse = createAccountWithVerifiedCredentials(responseJsonString, nonce)

    // Server returns the new account info (e.g., email, name)
    val claims = JSONObject(serverResponse.json)

    val userInfo = VerifiedUserInfo(
        email = claims.getString("email"),
        displayName = claims.optString("name", claims.getString("email"))
    )

    // handle response - Up to the developer
} catch (e: Exception) {
    // handle exceptions - Up to the developer
}

Passkey creation

An optional but highly recommended next step after provisioning an account is to immediately create a passkey for that account. This provides a secure, passwordless method for the user to sign in. This flow is identical to a standard passkey registration.

WebView support

For the flow to work on a WebView, developers should implement a JavaScript bridge (JS Bridge) to facilitate the handoff. This bridge allows the Webview to signal the native app, which can then perform the actual call to the Credential Manager API.