FHIR® Pseudonymizer

Send a FHIR® resource to /fhir/$de-identify get it back anonymized and/or pseudonymized.

Based on the brilliant Tools for Health Data Anonymization.

Usage

docker run --rm -i -p 8080:8080 \
  -e PseudonymizationService="None" \
  -e UseSystemTextJsonFhirSerializer="true" \
  ghcr.io/miracum/fhir-pseudonymizer:v2.22.1

curl -X POST -H "Content-Type:application/fhir+json" "http://localhost:8080/fhir/\$de-identify" -d @benchmark/observation.json

This uses the default anonymization config which only changes the sample Observation's id.

An example for deploying using (Docker) Compose can be found in the compose folder.

The recommended deployment is on Kubernetes. See https://github.com/miracum/charts/tree/master/charts/fhir-pseudonymizer for a Helm Chart.

API Endpoints

An OpenAPI definition for the FHIR operation endpoints is available at /swagger/:

$de-identify

The server provides a /fhir/$de-identify operation to de-identfiy received FHIR resources according to the configuration in the anonymization.yaml rules. See Tools for Health Data Anonymization for more details on the anonymization rule configuration.

The service comes with a sample configuration file to help meet the requirements of HIPAA Safe Harbor Method (2)(i): hipaa-anonymization.yaml.This configuration can be used by setting AnonymizationEngineConfigPath=/etc/hipaa-anonymization.yaml.

A new pseudonymize method was added to the default list of anonymization methods linked above. It uses either gPAS, Vfps, or entici to create pseudonyms and replace the values in the resource with them. For example, the following rule replaces all identifiers of type http://terminology.hl7.org/CodeSystem/v2-0203|MR with a pseudonym generated in the PATIENT domain.

fhirPathRules:
  - path: nodesByType('Identifier').where(type.coding.system='http://terminology.hl7.org/CodeSystem/v2-0203' and type.coding.code='MR').value
    method: pseudonymize
    domain: PATIENT

Note that if the domain setting is omitted, and an ID or reference is pseudonymized, then the resource name is used as the pseudonym domain. For example, pseudonymizing "reference": "Patient/123" will try to create a pseudonym for 123 in the Patient domain.

When using Vfps, the domain setting can instead also be set as namespace.

Note that all methods defined in Tools for Health Data Anonymization are supported. For example, to clamp a patient's birthdate if they were born before January 1st 1931 to 01/01/1930, use:

fhirPathRules:
  - path: Patient.birthDate
    method: generalize
    cases:
      "$this < @1931-01-01": "@1930-01-01"
    otherValues: keep

$de-pseudonymize

The /fhir/$de-pseudonymize operation is used to revert the pseudonymize and encrypt methods applied to any resource. Accessing this endpoint requires authentication. So make sure to set the APIKEY env var.

⚠ if decryption or de-pseudonymization of a value fails, then the original value is returned. This behavior may change or be made configurable in the future.

:8081/metrics

While not part of the "user" API, the application exposes metrics in the Prometheus format at the /metrics endpoint on port 8081.

Configuration

You can configure the anonymization and pseudonymization rules in the anonymization.yaml config file. It's mounted at /etc/anonymization.yaml within the container by default. See https://github.com/microsoft/FHIR-Tools-for-Anonymization for details on the syntax and options.

Additionally, there are some optional configuration values that can be set as environment variables:

Environment Variable	Description	Default
AnonymizationEngineConfigPath	Path to the anonymization.yaml that contains the rules to transform the resources.	"/etc/anonymization.yaml"
AnonymizationEngineConfigInline	The anonymization.yaml as an inline YAML string instead of a separate file. Takes precedence if both Path and Inline are set.	""
ApiKey	Key that must be set in the X-Api-Key header to allow requests to protected endpoints.	""
UseSystemTextJsonFhirSerializer	Enable the new System.Text.Json-based FHIR serializer to significantly improve throughput and latencies. See https://github.com/FirelyTeam/firely-net-sdk/releases/tag/v4.0.0-r4	false
PseudonymizationService	The type of pseudonymization service to use. Can be one of gPAS, Vfps, entici, None	"gPAS"
MetricsPort	The port where metrics in Prometheus format should be exposed at under the /metrics route.	8081
Anonymization__CryptoHashKey	Sets the key used by the HMAC SHA256 algorithm. This is an alternative to setting it inside the anonymization.yaml's parameters section and useful to more securely set sensitive information.	""
Anonymization__EncryptKey	Sets the AES encryption key. This is an alternative to setting it inside the anonymization.yaml's parameters section and useful to more securely set sensitive information.	""
Anonymization__ShouldAddSecurityTag	Whether the Resource.meta.security element should be filled with information about the de-identification methods applied to the resource.	true

See appsettings.json for additional options.

The application supports pseudonymization using either gPAS or Vfps which can be configured via the PseudonymizationService setting. Service-specific configuration settings are listed below.

gPAS

Environment Variable	Description	Default
gPAS__Url	The gPAS TTP FHIR Gateway URL. E.g. http://localhost:8080/ttp-fhir/fhir/gpas/ for gPAS 2023.1.0. Used if PseudonymizationService is set to gPAS.	""
gPAS__Version	Version of gPAS to support. There were breaking changes to the FHIR API in 1.10.2 and 1.10.3, so explicitely set this value if you are using a version newer than 1.10.1.	"1.10.1"

gPAS Basic Auth

Environment Variable	Description	Default
gPAS__Auth__Basic__Username	The HTTP basic auth username to connect to gPAS	""
gPAS__Auth__Basic__Password	The HTTP basic auth password to connect to gPAS	""

gPAS OAuth

Environment Variable	Description	Default
gPAS__Auth__OAuth__TokenEndpoint	The URL of the token endpoint	""
gPAS__Auth__OAuth__ClientId	The client ID	""
gPAS__Auth__OAuth__ClientSecret	The static (shared) client secret	""
gPAS__Auth__OAuth__Scope	The scope	""
gPAS__Auth__OAuth__Resource	The resource	""

Vfps

Environment Variable	Description	Default
Vfps__Address	The Vfps service address. Use dns:/// scheme for client-side load-balancing.	""
Vfps__UnsafeUseInsecureChannelCallCredentials	If set to true, CallCredentials are applied to gRPC calls made by an insecure channel. Sending authentication headers over an insecure connection has security implications and shouldn't be done in production environments.	true
Vfps__UseTls	If set to true, creates client-side SSL credentials loaded from disk file pointed to by the GRPC_DEFAULT_SSL_ROOTS_FILE_PATH environment variable. If that fails, gets the roots certificates from a well known place on disk.	false

Vfps Basic Auth

Environment Variable	Description	Default
Vfps__Auth__Basic__Username	The HTTP basic auth username to connect to the Vfps service. Used in the Authorization: Basic metadata header value for the gRPC calls.	""
Vfps__Auth__Basic__Password	The HTTP basic auth password to connect to the Vfps service.	""

entici

Environment Variable	Description	Default
entici__Url	The entici service base URL for FHIR operations. Used if PseudonymizationService is set to entici.	""

When using entici as a pseudonymization backend, you need to set additional settings for each rule that uses the pseudonymize method. These can be set under a entici section inside the anonymization config:

fhirPathRules:
  - path: nodesByType('Identifier').where(type.coding.where(system='http://terminology.hl7.org/CodeSystem/v2-0203' and code='MR').exists()).value
    method: pseudonymize
    # the domain will be used as the system of the identifier when invoking the entici pseudonymize operation
    domain: https://fhir.example.com/identifiers/patient-id
    entici:
      # the type of FHIR resource this pseudonym should be associated with
      resourceType: Patient
      # (optional) the project within entici the pseudonym is a part of
      project: some-internal-entici-project-name

entici OAuth

Environment Variable	Description	Default
entici__Auth__OAuth__TokenEndpoint	The URL of the token endpoint	""
entici__Auth__OAuth__ClientId	The client ID	""
entici__Auth__OAuth__ClientSecret	The static (shared) client secret	""
entici__Auth__OAuth__Scope	The scope	""
entici__Auth__OAuth__Resource	The resource	""

Truncating Crypto-hash Length

When using the cryptoHash method on a value, the result is a hex-encoded string of 64 characters length. You can truncate this to a specific maximum length using the truncateToMaxLength setting. For example:

fhirPathRules:
  - path: Resource.id
    method: cryptoHash
    truncateToMaxLength: 32

Will truncate the usually 64-character-long hash to the following:

{
  "resourceType": "Patient",
  "id": "b43a73c44e6d5b57644b63d89ee90cbf"
}

Dynamic rule settings

Anonymization and pseudonymization rules in the anonymization.yaml config file can be overridden and/or extended on a per request basis.

Pseudonymization supports a domain-prefix rule setting which can be used to dynamically configure the target domain by providing its value as part of the request body.

The following example shows how to use this feature to use a single service configuration in order to support multiple projects which have the same basic domain names, prefixed by a project name.

Example

gPAS domains for patient IDs:

project	domain
miracum	miracum-patient
test	test-patient

anonymization.yml:

---
fhirVersion: R4
fhirPathRules:
  - path: nodesByType('Identifier').where(type.coding.system='http://terminology.hl7.org/CodeSystem/v2-0203' and type.coding.code='MR').value
    method: pseudonymize
    domain: patient

Providing the prefix (i.e. miracum- or test-) via the request, pseudonymization can be done with the same rules for different projects.

Request body

Rule settings can be provided by using the Parameters resource with a settings parameter and parts consisting of the settings key and value. The resource parameter must contain the actual target resource.

The following request body and the (fixed) configuration settings above will result in the target domain miracum-patient.

{
  "resourceType": "Parameters",
  "parameter": [
    {
      "name": "settings",
      "part": [
        {
          "name": "domain-prefix",
          "valueString": "miracum-"
        }
      ]
    },
    {
      "name": "resource",
      "resource": {
        "resourceType": "Bundle",
        "type": "transaction",
        "entry": [
          {
            "fullUrl": "urn:uuid:3bc44de3-069d-442d-829b-f3ef68cae371",
            "resource": {
              "resourceType": "Patient",
              "identifier": [
                {
                  "type": {
                    "coding": [
                      {
                        "system": "http://terminology.hl7.org/CodeSystem/v2-0203",
                        "code": "MR"
                      }
                    ]
                  },
                  "system": "http://acme.org/mrns",
                  "value": "12345"
                }
              ],
              "name": [
                {
                  "family": "Jameson",
                  "given": ["J", "Jonah"]
                }
              ],
              "gender": "male"
            },
            "request": {
              "method": "POST",
              "url": "Patient/12345"
            }
          }
        ]
      }
    }
  ]
}

Note: The domain name could also have been replaced completely by overriding the domain setting with the desired value. This works for all rule settings regardless of the method value.

Development

Start Development Fixtures (optional)

To test Vfps and tracing via Jaeger, run

docker compose -f compose.dev.yaml up

to also start a Keycloak instance with pre-configured fhir-pseudonymizer client, set --profile=keycloak:

docker compose -f compose.dev.yaml --profile=keycloak up

Build

dotnet restore
dotnet build

Or using Docker:

docker build -t ghcr.io/miracum/fhir-pseudonymizer:local-build .

Run

dotnet run --project src/FhirPseudonymizer

Test

dotnet test src/FhirPseudonymizer.Tests/

Install Pre-commit Hooks

pre-commit install
pre-commit install --hook-type commit-msg

Run iter8 SLO experiments locally

ITER8_CLI_URL="https://github.com/iter8-tools/iter8/releases/download/v0.13.18/iter8-linux-amd64.tar.gz"
curl -LSs "${ITER8_CLI_URL}" | tar xz
mv linux-amd64/iter8 /usr/local/bin/iter8
chmod +x /usr/local/bin/iter8
iter8 version

kind create cluster

export IMAGE_TAG="iter8-test"

docker build -t ghcr.io/miracum/fhir-pseudonymizer:${IMAGE_TAG} .

kind load docker-image ghcr.io/miracum/fhir-pseudonymizer:${IMAGE_TAG}

helm upgrade --install \
  --set="image.tag=${IMAGE_TAG}" \
  -f tests/iter8/values.yaml \
  --wait \
  --timeout=10m \
  fhir-pseudonymizer oci://ghcr.io/miracum/charts/fhir-pseudonymizer

kubectl apply -f tests/iter8/experiment.yaml

iter8 k assert -c completed --timeout 15m
iter8 k assert -c nofailure,slos
iter8 k report

# to restart:
kubectl delete job default-1-job
kubectl apply -f tests/iter8/experiment.yaml

Benchmark

Note Example runs were conducted on the following hardware:

OS=Windows 11 (10.0.22000.978/21H2)
12th Gen Intel Core i9-12900K, 1 CPU, 24 logical and 16 physical cores
32GiB of DDR5 4800MHz RAM
Samsung SSD 980 Pro 1TiB
.NET SDK=7.0.101

Prerequisites: https://github.com/codesenberg/bombardier

dotnet run -c Release --project=src/FhirPseudonymizer

In a different terminal

cd benchmark/
$ ./bombardier.sh

Bombarding http://localhost:5000/fhir/$de-identify for 1m0s using 125 connection(s)
[====================================================================================================================] 1m0s
Done!
Statistics        Avg      Stdev        Max
  Reqs/sec     13107.78    1552.49   18917.77
  Latency        9.53ms   559.41us    53.88ms
  Latency Distribution
     50%     9.00ms
     75%    11.00ms
     90%    12.00ms
     95%    13.00ms
     99%    16.73ms
  HTTP codes:
    1xx - 0, 2xx - 786655, 3xx - 0, 4xx - 0, 5xx - 0
    others - 0
  Throughput:    96.37MB/s

UseSystemTextJsonFhirSerializer

You can improve throughput and P99 latencies by opting-in to using the System.Text.Json based FHIR resource serializer. It can be enabled via appsettings.json or using the UseSystemTextJsonFhirSerializer environment variable:

UseSystemTextJsonFhirSerializer=true dotnet run -c Release --project=src/FhirPseudonymizer

Bombarding http://localhost:5000/fhir/$de-identify for 1m0s using 125 connection(s)
[====================================================================================================================] 1m0s
Done!
Statistics        Avg      Stdev        Max
  Reqs/sec     21508.39    3751.90   38993.50
  Latency        5.80ms     1.63ms   442.82ms
  Latency Distribution
     50%     5.00ms
     75%     6.00ms
     90%     7.75ms
     95%     9.00ms
     99%    12.00ms
  HTTP codes:
    1xx - 0, 2xx - 1291159, 3xx - 0, 4xx - 0, 5xx - 0
    others - 0
  Throughput:   158.17MB/s

Image signature and provenance verification

Prerequisites:

• cosign
• slsa-verifier
• crane

All released container images are signed using cosign and SLSA Level 3 provenance is available for verification.

IMAGE=ghcr.io/miracum/fhir-pseudonymizer:v2.22.1
DIGEST=$(crane digest "${IMAGE}")
IMAGE_DIGEST_PINNED="ghcr.io/miracum/fhir-pseudonymizer@${DIGEST}"
IMAGE_TAG="${IMAGE#*:}"

cosign verify \
   --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
   --certificate-identity-regexp="https://github.com/miracum/.github/.github/workflows/standard-build.yaml@.*" \
   --certificate-github-workflow-name="ci" \
   --certificate-github-workflow-repository="miracum/fhir-pseudonymizer" \
   --certificate-github-workflow-trigger="release" \
   --certificate-github-workflow-ref="refs/tags/${IMAGE_TAG}" \
   "${IMAGE_DIGEST_PINNED}"

slsa-verifier verify-image \
    --source-uri github.com/miracum/fhir-pseudonymizer \
    --source-tag ${IMAGE_TAG} \
    --source-branch master \
    "${IMAGE_DIGEST_PINNED}"

Semantic versioning exclusion policies

The project's versioning follows the SemVer convention. However, we exclude metrics (ie. anything under the :8081/metrics endpoint), traces, and the contents of the container image from this. Always be prepared to double-check the release notes before updating.

Attribution

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