Henry Borasch
--- a/core/src/test/java/dev/fitko/fitconnect/core/validation/DefaultValidationServiceTest.java
+++ b/core/src/test/java/dev/fitko/fitconnect/core/validation/DefaultValidationServiceTest.java

        // Then
        assertTrue(validationResult.hasError());
-        assertThat(validationResult.getError().getMessage(), containsString("\"certChain\" is null"));
+        assertThat(validationResult.getError().getMessage(), containsString("\"x5c\" is null"));
--- a/core/src/main/java/dev/fitko/fitconnect/core/util/FileUtil.java 0 → 100644
+++ b/core/src/main/java/dev/fitko/fitconnect/core/util/FileUtil.java 0 → 100644
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class FileUtil {
+
+    public static List<String> loadContentOfFilesInDirectory(String directoryPath) {
+
+        File folder = new File(Objects.requireNonNull(FileUtil.class.getClassLoader().getResource(directoryPath)).getFile());
+
+        return Arrays.stream(Objects.requireNonNull(folder.listFiles())).map(file -> {
+            try {
+                return Files.readString(file.toPath());
--- a/core/src/main/java/dev/fitko/fitconnect/core/util/FileUtil.java 0 → 100644
+++ b/core/src/main/java/dev/fitko/fitconnect/core/util/FileUtil.java 0 → 100644
+
+        return Arrays.stream(Objects.requireNonNull(folder.listFiles())).map(file -> {
+            try {
+                return Files.readString(file.toPath());
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }).collect(Collectors.toList());
+    }
+
+    public static String loadContentOfFile(String filePath) {
+
+        try {
+            return Files.readString(new File(Objects.requireNonNull(FileUtil.class.getClassLoader().getResource(filePath)).getFile()).toPath());
+        } catch (IOException e) {
+            throw new RuntimeException(e);
--- a/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
+++ b/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
    private static final Logger LOGGER = LoggerFactory.getLogger(DefaultValidationService.class);
    private static final ObjectMapper MAPPER = new ObjectMapper().setDateFormat(new SimpleDateFormat("yyyy-MM-dd"));
    private static final JsonSchemaFactory SCHEMA_FACTORY = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V202012);
-    public static final String VALID_SCHEMA_URL_EXPRESSION = "https://schema\\.fitko\\.de/fit-connect/metadata/1\\.\\d+\\.\\d+/metadata.schema.json";
+    private static final String VALID_SCHEMA_URL_EXPRESSION = "https://schema\\.fitko\\.de/fit-connect/metadata/1\\.\\d+\\.\\d+/metadata.schema.json";

    private final MessageDigestService messageDigestService;
    private final SchemaProvider schemaProvider;
    private final ApplicationConfig config;
+    private final String pathToTrustedRootCertificates;

-    public DefaultValidationService(final ApplicationConfig config, final MessageDigestService messageDigestService, final SchemaProvider schemaProvider) {
+    public DefaultValidationService(final ApplicationConfig config, final MessageDigestService messageDigestService,
+                                    final SchemaProvider schemaProvider, final String pathToTrustedRootCertificates) {
--- a/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
+++ b/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
+            validateWithX509AndWithoutProxy(trustedRootCertificates, publicKey, purpose);
        }
    }

-    private List<String> getPemCerts(final List<X509Certificate> certChain) throws CertificateEncodingException {
-        final List<String> pemCerts = new ArrayList<>();
-        for (final X509Certificate cert : certChain) {
-            pemCerts.add(getEncodedString(cert));
-        }
-        return pemCerts;
-    }
+    private List<String> loadTrustedRootCertificates() {
+
+        List<X509Certificate> trustedRootCertificates = FileUtil.loadContentOfFilesInDirectory(this.pathToTrustedRootCertificates)
+                .stream().map(FileUtil::convertToX509Certificate).collect(Collectors.toList());
+        List<String> encodedCertificates = trustedRootCertificates.stream().map(cert -> {
--- a/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
+++ b/core/src/main/java/dev/fitko/fitconnect/core/validation/DefaultValidationService.java
        } else {
-            validateWithX509AndWithoutProxy(pemCerts, publicKey, purpose);
+            validateWithX509AndWithoutProxy(trustedRootCertificates, publicKey, purpose);
        }
    }

-    private List<String> getPemCerts(final List<X509Certificate> certChain) throws CertificateEncodingException {
-        final List<String> pemCerts = new ArrayList<>();
-        for (final X509Certificate cert : certChain) {
-            pemCerts.add(getEncodedString(cert));
-        }
-        return pemCerts;
-    }
+    private List<String> loadTrustedRootCertificates() {
+
+        List<String> trustedRootCertificates = rootCertificates.stream()