googleapis/google/cloud/confidentialcomputing/v1/service.proto

// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.cloud.confidentialcomputing.v1;

import "google/api/annotations.proto";
import "google/api/client.proto";
import "google/api/field_behavior.proto";
import "google/api/resource.proto";
import "google/protobuf/timestamp.proto";
import "google/rpc/status.proto";

option csharp_namespace = "Google.Cloud.ConfidentialComputing.V1";
option go_package = "cloud.google.com/go/confidentialcomputing/apiv1/confidentialcomputingpb;confidentialcomputingpb";
option java_multiple_files = true;
option java_outer_classname = "ServiceProto";
option java_package = "com.google.cloud.confidentialcomputing.v1";
option php_namespace = "Google\\Cloud\\ConfidentialComputing\\V1";
option ruby_package = "Google::Cloud::ConfidentialComputing::V1";

// Service describing handlers for resources
service ConfidentialComputing {
  option (google.api.default_host) = "confidentialcomputing.googleapis.com";
  option (google.api.oauth_scopes) =
      "https://www.googleapis.com/auth/cloud-platform";

  // Creates a new Challenge in a given project and location.
  rpc CreateChallenge(CreateChallengeRequest) returns (Challenge) {
    option (google.api.http) = {
      post: "/v1/{parent=projects/*/locations/*}/challenges"
      body: "challenge"
    };
    option (google.api.method_signature) = "parent,challenge";
  }

  // Verifies the provided attestation info, returning a signed attestation
  // token.
  rpc VerifyAttestation(VerifyAttestationRequest)
      returns (VerifyAttestationResponse) {
    option (google.api.http) = {
      post: "/v1/{challenge=projects/*/locations/*/challenges/*}:verifyAttestation"
      body: "*"
    };
  }

  // Verifies whether the provided attestation info is valid, returning a signed
  // attestation token if so.
  rpc VerifyConfidentialSpace(VerifyConfidentialSpaceRequest)
      returns (VerifyConfidentialSpaceResponse) {
    option (google.api.http) = {
      post: "/v1/{challenge=projects/*/locations/*/challenges/*}:verifyConfidentialSpace"
      body: "*"
    };
  }

  // Verifies the provided Confidential GKE attestation info, returning a signed
  // OIDC token.
  rpc VerifyConfidentialGke(VerifyConfidentialGkeRequest)
      returns (VerifyConfidentialGkeResponse) {
    option (google.api.http) = {
      post: "/v1/{challenge=projects/*/locations/*/challenges/*}:verifyConfidentialGke"
      body: "*"
    };
  }
}

// SigningAlgorithm enumerates all the supported signing algorithms.
enum SigningAlgorithm {
  // Unspecified signing algorithm.
  SIGNING_ALGORITHM_UNSPECIFIED = 0;

  // RSASSA-PSS with a SHA256 digest.
  RSASSA_PSS_SHA256 = 1;

  // RSASSA-PKCS1 v1.5 with a SHA256 digest.
  RSASSA_PKCS1V15_SHA256 = 2;

  // ECDSA on the P-256 Curve with a SHA256 digest.
  ECDSA_P256_SHA256 = 3;
}

// Token type enum contains the different types of token responses Confidential
// Space supports
enum TokenType {
  // Unspecified token type
  TOKEN_TYPE_UNSPECIFIED = 0;

  // OpenID Connect (OIDC) token type
  TOKEN_TYPE_OIDC = 1;

  // Public Key Infrastructure (PKI) token type
  TOKEN_TYPE_PKI = 2;

  // Limited claim token type for AWS integration
  TOKEN_TYPE_LIMITED_AWS = 3;

  // Principal-tag-based token for AWS integration
  TOKEN_TYPE_AWS_PRINCIPALTAGS = 4;
}

// SignatureType enumerates supported signature types for attestation tokens.
enum SignatureType {
  // Unspecified signature type.
  SIGNATURE_TYPE_UNSPECIFIED = 0;

  // Google OIDC signature.
  SIGNATURE_TYPE_OIDC = 1;

  // Public Key Infrastructure (PKI) signature.
  SIGNATURE_TYPE_PKI = 2;
}

// TokenProfile enumerates the supported token claims profiles.
enum TokenProfile {
  // Unspecified token profile.
  TOKEN_PROFILE_UNSPECIFIED = 0;

  // EAT claims.
  TOKEN_PROFILE_DEFAULT_EAT = 1;

  // AWS Principal Tags claims.
  TOKEN_PROFILE_AWS = 2;
}

// A Challenge from the server used to guarantee freshness of attestations
message Challenge {
  option (google.api.resource) = {
    type: "confidentialcomputing.googleapis.com/Challenge"
    pattern: "projects/{project}/locations/{location}/challenges/{uuid}"
  };

  // Output only. The resource name for this Challenge in the format
  // `projects/*/locations/*/challenges/*`
  string name = 1 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. The time at which this Challenge was created
  google.protobuf.Timestamp create_time = 2
      [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. The time at which this Challenge will no longer be usable. It
  // is also the expiration time for any tokens generated from this Challenge.
  google.protobuf.Timestamp expire_time = 3
      [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. Indicates if this challenge has been used to generate a token.
  bool used = 4 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. Identical to nonce, but as a string.
  string tpm_nonce = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
}

// Message for creating a Challenge
message CreateChallengeRequest {
  // Required. The resource name of the location where the Challenge will be
  // used, in the format `projects/*/locations/*`.
  string parent = 1 [
    (google.api.field_behavior) = REQUIRED,
    (google.api.resource_reference) = {
      type: "locations.googleapis.com/Location"
    }
  ];

  // Required. The Challenge to be created. Currently this field can be empty as
  // all the Challenge fields are set by the server.
  Challenge challenge = 2 [(google.api.field_behavior) = REQUIRED];
}

// A request for an attestation token, providing all the necessary information
// needed for this service to verify the platform state of the requestor.
message VerifyAttestationRequest {
  // An optional tee attestation report, used to populate hardware rooted
  // claims.
  oneof tee_attestation {
    // Optional. A TDX with CCEL and RTMR Attestation Quote.
    TdxCcelAttestation td_ccel = 6 [(google.api.field_behavior) = OPTIONAL];

    // Optional. An SEV-SNP Attestation Report.
    SevSnpAttestation sev_snp_attestation = 7
        [(google.api.field_behavior) = OPTIONAL];
  }

  // An optional device attestation report.
  oneof device_attestation {
    // Optional. An Nvidia attestation report for GPU and NVSwitch devices.
    NvidiaAttestation nvidia_attestation = 9
        [(google.api.field_behavior) = OPTIONAL];
  }

  // Required. The name of the Challenge whose nonce was used to generate the
  // attestation, in the format `projects/*/locations/*/challenges/*`. The
  // provided Challenge will be consumed, and cannot be used again.
  string challenge = 1 [
    (google.api.field_behavior) = REQUIRED,
    (google.api.resource_reference) = {
      type: "confidentialcomputing.googleapis.com/Challenge"
    }
  ];

  // Optional. Credentials used to populate the "emails" claim in the
  // claims_token.
  GcpCredentials gcp_credentials = 2 [(google.api.field_behavior) = OPTIONAL];

  // Required. The TPM-specific data provided by the attesting platform, used to
  // populate any of the claims regarding platform state.
  TpmAttestation tpm_attestation = 3 [(google.api.field_behavior) = REQUIRED];

  // Optional. Optional information related to the Confidential Space TEE.
  ConfidentialSpaceInfo confidential_space_info = 4
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. A collection of optional, workload-specified claims that modify
  // the token output.
  TokenOptions token_options = 5 [(google.api.field_behavior) = OPTIONAL];

  // Optional. An optional indicator of the attester, only applies to certain
  // products.
  string attester = 8 [(google.api.field_behavior) = OPTIONAL];
}

// An Nvidia attestation report for GPU and NVSwitch devices.
// Contains necessary attestation evidence that the client collects for
// verification.
message NvidiaAttestation {
  // GpuInfo contains the attestation evidence for a GPU device.
  message GpuInfo {
    // Optional. The UUID of the GPU device.
    string uuid = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. The driver version of the GPU.
    string driver_version = 2 [(google.api.field_behavior) = OPTIONAL];

    // Optional. The vBIOS version of the GPU.
    string vbios_version = 3 [(google.api.field_behavior) = OPTIONAL];

    // Optional. The GPU architecture type.
    GpuArchitectureType gpu_architecture_type = 4
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. The raw attestation certificate chain for the GPU device.
    bytes attestation_certificate_chain = 5
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. The raw attestation report for the GPU device.
    // This field contains SPDM request/response defined in
    // https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.1.0.pdf
    bytes attestation_report = 6 [(google.api.field_behavior) = OPTIONAL];
  }

  // SwitchInfo contains the attestation evidence for a NVSwitch device.
  message SwitchInfo {
    // Optional. The UUID of the NVSwitch device.
    string uuid = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. The raw attestation certificate chain for the NVSwitch device.
    bytes attestation_certificate_chain = 2
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. The raw attestation report for the NvSwitch device.
    // This field contains SPDM request/response defined in
    // https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.1.0.pdf
    bytes attestation_report = 3 [(google.api.field_behavior) = OPTIONAL];
  }

  // Single GPU Passthrough (SPT) attestation.
  message SinglePassthroughAttestation {
    // Optional. Single GPU quote.
    GpuInfo gpu_quote = 1 [(google.api.field_behavior) = OPTIONAL];
  }

  // Protected PCIe (PPCIE) attestation.
  // Eight Hopper GPUs with Four NVSwitch Passthrough.
  message ProtectedPcieAttestation {
    // Optional. A list of GPU infos.
    repeated GpuInfo gpu_quotes = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. A list of SWITCH infos.
    repeated SwitchInfo switch_quotes = 2
        [(google.api.field_behavior) = OPTIONAL];
  }

  // MultiGpuSecurePassthroughAttestation contains the attestation evidence
  // for a Multi-GPU Secure Passthrough (MPT) attestation.
  message MultiGpuSecurePassthroughAttestation {
    // Optional. A list of GPU quotes.
    repeated GpuInfo gpu_quotes = 1 [(google.api.field_behavior) = OPTIONAL];
  }

  // GpuArchitectureType enumerates the supported GPU architecture types.
  enum GpuArchitectureType {
    // Unspecified GPU architecture type.
    GPU_ARCHITECTURE_TYPE_UNSPECIFIED = 0;

    // Hopper GPU architecture type.
    GPU_ARCHITECTURE_TYPE_HOPPER = 8;

    // Blackwell GPU architecture type.
    GPU_ARCHITECTURE_TYPE_BLACKWELL = 10;
  }

  // The Confidential Computing feature that the attestation is for.
  oneof cc_feature {
    // Single GPU Passthrough (SPT) attestation.
    SinglePassthroughAttestation spt = 1;

    // Protected PCIe (PPCIE) attestation.
    ProtectedPcieAttestation ppcie = 2;

    // Multi-GPU Secure Passthrough (MPT) attestation.
    MultiGpuSecurePassthroughAttestation mpt = 3;
  }
}

// A TDX Attestation quote.
message TdxCcelAttestation {
  // Optional. The Confidential Computing Event Log (CCEL) ACPI table. Formatted
  // as described in the ACPI Specification 6.5.
  bytes ccel_acpi_table = 1 [(google.api.field_behavior) = OPTIONAL];

  // Optional. The CCEL event log. Formatted as described in the UEFI 2.10.
  bytes ccel_data = 2 [(google.api.field_behavior) = OPTIONAL];

  // Optional. An Event Log containing additional events measured into the RTMR
  // that are not already present in the CCEL.
  bytes canonical_event_log = 3 [(google.api.field_behavior) = OPTIONAL];

  // Optional. The TDX attestation quote from the guest. It contains the RTMR
  // values.
  bytes td_quote = 4 [(google.api.field_behavior) = OPTIONAL];
}

// An SEV-SNP Attestation Report.
// Contains the attestation report and the certificate bundle that the client
// collects.
message SevSnpAttestation {
  // Optional. The SEV-SNP Attestation Report
  // Format is in revision 1.55, §7.3 Attestation, Table 22. ATTESTATION_REPORT
  // Structure in this document:
  // https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56860.pdf
  bytes report = 1 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Certificate bundle defined in the GHCB protocol definition
  // Format is documented in GHCB revision 2.03, section 4.1.8.1 struct
  // cert_table in this document:
  // https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf
  bytes aux_blob = 2 [(google.api.field_behavior) = OPTIONAL];
}

// A response once an attestation has been successfully verified, containing a
// signed attestation token.
message VerifyAttestationResponse {
  // Output only. Same as claims_token, but as a string.
  string oidc_claims_token = 2 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. A list of messages that carry the partial error details
  // related to VerifyAttestation.
  repeated google.rpc.Status partial_errors = 3
      [(google.api.field_behavior) = OUTPUT_ONLY];
}

// Credentials issued by GCP which are linked to the platform attestation. These
// will be verified server-side as part of attestaion verification.
message GcpCredentials {
  // Same as id_tokens, but as a string.
  repeated string service_account_id_tokens = 2;
}

// Options to modify claims in the token to generate custom-purpose tokens.
message TokenOptions {
  // An optional additional configuration per token type.
  oneof token_type_options {
    // Optional. Options for AWS token type.
    AwsPrincipalTagsOptions aws_principal_tags_options = 4
        [(google.api.field_behavior) = OPTIONAL];
  }

  // Optional. Optional string to issue the token with a custom audience claim.
  // Required if one or more nonces are specified.
  string audience = 1 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Optional parameter to place one or more nonces in the eat_nonce
  // claim in the output token. The minimum size for JSON-encoded EATs is 10
  // bytes and the maximum size is 74 bytes.
  repeated string nonce = 2 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Optional token type to select what type of token to return.
  TokenType token_type = 3 [(google.api.field_behavior) = OPTIONAL];
}

// Token options that only apply to the AWS Principal Tags token type.
message AwsPrincipalTagsOptions {
  // Allowed principal tags is used to define what principal tags will be
  // placed in the token.
  message AllowedPrincipalTags {
    // Allowed Container Image Signatures. Key IDs are required to allow
    // this claim to fit within the narrow AWS IAM restrictions.
    message ContainerImageSignatures {
      // Optional. List of key ids to filter into the Principal tags. Only keys
      // that have been validated and added to the token will be filtered into
      // principal tags. Unrecognized key ids will be ignored.
      repeated string key_ids = 1 [(google.api.field_behavior) = OPTIONAL];
    }

    // Optional. Container image signatures allowed in the token.
    ContainerImageSignatures container_image_signatures = 1
        [(google.api.field_behavior) = OPTIONAL];
  }

  // Optional. Principal tags to allow in the token.
  AllowedPrincipalTags allowed_principal_tags = 1
      [(google.api.field_behavior) = OPTIONAL];
}

// TPM2 data containing everything necessary to validate any platform state
// measured into the TPM.
message TpmAttestation {
  // Information about Platform Control Registers (PCRs) including a signature
  // over their values, which can be used for remote validation.
  message Quote {
    // The hash algorithm of the PCR bank being quoted, encoded as a TPM_ALG_ID
    int32 hash_algo = 1;

    // Raw binary values of each PCRs being quoted.
    map<int32, bytes> pcr_values = 2;

    // TPM2 quote, encoded as a TPMS_ATTEST
    bytes raw_quote = 3;

    // TPM2 signature, encoded as a TPMT_SIGNATURE
    bytes raw_signature = 4;
  }

  // TPM2 PCR Quotes generated by calling TPM2_Quote on each PCR bank.
  repeated Quote quotes = 1;

  // The binary TCG Event Log containing events measured into the TPM by the
  // platform firmware and operating system. Formatted as described in the
  // "TCG PC Client Platform Firmware Profile Specification".
  bytes tcg_event_log = 2;

  // An Event Log containing additional events measured into the TPM that are
  // not already present in the tcg_event_log. Formatted as described in the
  // "Canonical Event Log Format" TCG Specification.
  bytes canonical_event_log = 3;

  // DER-encoded X.509 certificate of the Attestation Key (otherwise known as
  // an AK or a TPM restricted signing key) used to generate the quotes.
  bytes ak_cert = 4;

  // List of DER-encoded X.509 certificates which, together with the ak_cert,
  // chain back to a trusted Root Certificate.
  repeated bytes cert_chain = 5;
}

// ConfidentialSpaceInfo contains information related to the Confidential Space
// TEE.
message ConfidentialSpaceInfo {
  // Optional. A list of signed entities containing container image signatures
  // that can be used for server-side signature verification.
  repeated SignedEntity signed_entities = 1
      [(google.api.field_behavior) = OPTIONAL];
}

// SignedEntity represents an OCI image object containing everything necessary
// to verify container image signatures.
message SignedEntity {
  // Optional. A list of container image signatures attached to an OCI image
  // object.
  repeated ContainerImageSignature container_image_signatures = 1
      [(google.api.field_behavior) = OPTIONAL];
}

// ContainerImageSignature holds necessary metadata to verify a container image
// signature.
message ContainerImageSignature {
  // Optional. The binary signature payload following the SimpleSigning format
  // https://github.com/sigstore/cosign/blob/main/specs/SIGNATURE_SPEC.md#simple-signing.
  // This payload includes the container image digest.
  bytes payload = 1 [(google.api.field_behavior) = OPTIONAL];

  // Optional. A signature over the payload.
  // The container image digest is incorporated into the signature as follows:
  // 1. Generate a SimpleSigning format payload that includes the container
  // image digest.
  // 2. Generate a signature over SHA256 digest of the payload.
  // The signature generation process can be represented as follows:
  // `Sign(sha256(SimpleSigningPayload(sha256(Image Manifest))))`
  bytes signature = 2 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Reserved for future use.
  bytes public_key = 3 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Reserved for future use.
  SigningAlgorithm sig_alg = 4 [(google.api.field_behavior) = OPTIONAL];
}

// A request for an attestation token, providing all the necessary information
// needed for this service to verify the platform state of the requestor.
message VerifyConfidentialSpaceRequest {
  // Token options for Confidential Space attestation.
  message ConfidentialSpaceOptions {
    // An optional additional configuration per token type.
    oneof token_profile_options {
      // Optional. Options for the AWS token type.
      AwsPrincipalTagsOptions aws_principal_tags_options = 5
          [(google.api.field_behavior) = OPTIONAL];
    }

    // Optional. Optional string to issue the token with a custom audience
    // claim. Required if custom nonces are specified.
    string audience = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Optional specification for token claims profile.
    TokenProfile token_profile = 2 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Optional parameter to place one or more nonces in the eat_nonce
    // claim in the output token. The minimum size for JSON-encoded EATs is 10
    // bytes and the maximum size is 74 bytes.
    repeated string nonce = 3 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Optional specification for how to sign the attestation token.
    // Defaults to SIGNATURE_TYPE_OIDC if unspecified.
    SignatureType signature_type = 4 [(google.api.field_behavior) = OPTIONAL];
  }

  // Required. A tee attestation report, used to populate hardware rooted
  // claims.
  oneof tee_attestation {
    // Input only. A TDX with CCEL and RTMR Attestation Quote.
    TdxCcelAttestation td_ccel = 3 [(google.api.field_behavior) = INPUT_ONLY];

    // Input only. The TPM-specific data provided by the attesting platform,
    // used to populate any of the claims regarding platform state.
    TpmAttestation tpm_attestation = 4
        [(google.api.field_behavior) = INPUT_ONLY];
  }

  // Required. The name of the Challenge whose nonce was used to generate the
  // attestation, in the format `projects/*/locations/*/challenges/*`. The
  // provided Challenge will be consumed, and cannot be used again.
  string challenge = 1 [
    (google.api.field_behavior) = REQUIRED,
    (google.api.resource_reference) = {
      type: "confidentialcomputing.googleapis.com/Challenge"
    }
  ];

  // Optional. Credentials used to populate the "emails" claim in the
  // claims_token. If not present, token will not contain the "emails" claim.
  GcpCredentials gcp_credentials = 2 [(google.api.field_behavior) = OPTIONAL];

  // Optional. A list of signed entities containing container image signatures
  // that can be used for server-side signature verification.
  repeated SignedEntity signed_entities = 5
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. Information about the associated Compute Engine instance.
  // Required for td_ccel requests only - tpm_attestation requests will provide
  // this information in the attestation.
  GceShieldedIdentity gce_shielded_identity = 6
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. A collection of fields that modify the token output.
  ConfidentialSpaceOptions options = 7 [(google.api.field_behavior) = OPTIONAL];

  // Optional. An optional Nvidia attestation report, used to populate hardware
  // rooted claims for Nvidia devices.
  NvidiaAttestation nvidia_attestation = 8
      [(google.api.field_behavior) = OPTIONAL];
}

// GceShieldedIdentity contains information about a Compute Engine instance.
message GceShieldedIdentity {
  // Optional. DER-encoded X.509 certificate of the Attestation Key (otherwise
  // known as an AK or a TPM restricted signing key) used to generate the
  // quotes.
  bytes ak_cert = 1 [(google.api.field_behavior) = OPTIONAL];

  // Optional. List of DER-encoded X.509 certificates which, together with the
  // ak_cert, chain back to a trusted Root Certificate.
  repeated bytes ak_cert_chain = 2 [(google.api.field_behavior) = OPTIONAL];
}

// VerifyConfidentialSpaceResponse is returned once a Confidential Space
// attestation has been successfully verified, containing a signed token.
message VerifyConfidentialSpaceResponse {
  // Output only. The attestation token issued by this service. It contains
  // specific platform claims based on the contents of the provided attestation.
  string attestation_token = 1 [(google.api.field_behavior) = OUTPUT_ONLY];

  // Output only. A list of messages that carry the partial error details
  // related to VerifyConfidentialSpace. This field is populated by errors
  // during container image signature verification, which may reflect problems
  // in the provided image signatures. This does not block the issuing of an
  // attestation token, but the token will not contain claims for the failed
  // image signatures.
  repeated google.rpc.Status partial_errors = 2
      [(google.api.field_behavior) = OUTPUT_ONLY];
}

// A request for an attestation token, providing all the necessary information
// needed for this service to verify Confidential GKE platform state of the
// requestor.
message VerifyConfidentialGkeRequest {
  // Token options for Confidential GKE attestation.
  message ConfidentialGkeOptions {
    // Optional. Optional string to issue the token with a custom audience
    // claim. Required if custom nonces are specified.
    string audience = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Optional parameter to place one or more nonces in the eat_nonce
    // claim in the output token. The minimum size for JSON-encoded EATs is 10
    // bytes and the maximum size is 74 bytes.
    repeated string nonce = 3 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Optional specification for how to sign the attestation token.
    // Defaults to SIGNATURE_TYPE_OIDC if unspecified.
    SignatureType signature_type = 4 [(google.api.field_behavior) = OPTIONAL];
  }

  // Required. A tee attestation report, used to populate hardware rooted
  // claims.
  oneof tee_attestation {
    // The TPM-specific data provided by the attesting platform, used to
    // populate any of the claims regarding platform state.
    TpmAttestation tpm_attestation = 2;
  }

  // Required. The name of the Challenge whose nonce was used to generate the
  // attestation, in the format projects/*/locations/*/challenges/*. The
  // provided Challenge will be consumed, and cannot be used again.
  string challenge = 1 [
    (google.api.field_behavior) = REQUIRED,
    (google.api.resource_reference) = {
      type: "confidentialcomputing.googleapis.com/Challenge"
    }
  ];

  // Optional. A collection of fields that modify the token output.
  ConfidentialGkeOptions options = 3 [(google.api.field_behavior) = OPTIONAL];
}

// VerifyConfidentialGkeResponse response is returened once a Confidential GKE
// attestation has been successfully verified, containing a signed OIDC token.
message VerifyConfidentialGkeResponse {
  // Output only. The attestation token issued by this service for Confidential
  // GKE. It contains specific platform claims based on the contents of the
  // provided attestation.
  string attestation_token = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
}