diff --git a/pom.xml b/pom.xml
index 9739035..ff4bc68 100644
--- a/pom.xml
+++ b/pom.xml
@@ -19,7 +19,7 @@
 	<properties>
 		<java.version>17</java.version>
 		<maven-surefire-plugin.version>3.2.5</maven-surefire-plugin.version>
-		<webeid.version>3.0.1</webeid.version>
+		<webeid.version>3.0.2-SNAPSHOT</webeid.version>
 		<digidoc4j.version>5.3.0</digidoc4j.version>
 		<jmockit.version>1.44</jmockit.version>
 		<jib.version>3.4.2</jib.version>
diff --git a/src/main/java/eu/webeid/example/security/WebEidAuthentication.java b/src/main/java/eu/webeid/example/security/WebEidAuthentication.java
index 59ab2a7..c039007 100644
--- a/src/main/java/eu/webeid/example/security/WebEidAuthentication.java
+++ b/src/main/java/eu/webeid/example/security/WebEidAuthentication.java
@@ -22,15 +22,16 @@
 
 package eu.webeid.example.security;
 
+import eu.webeid.security.certificate.CertificateData;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationToken;
-import eu.webeid.security.certificate.CertificateData;
 
 import java.security.cert.CertificateEncodingException;
 import java.security.cert.X509Certificate;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 
 public class WebEidAuthentication extends PreAuthenticatedAuthenticationToken implements Authentication {
 
@@ -38,7 +39,8 @@ public class WebEidAuthentication extends PreAuthenticatedAuthenticationToken im
 
     public static Authentication fromCertificate(X509Certificate userCertificate, List<GrantedAuthority> authorities) throws CertificateEncodingException {
         final String principalName = getPrincipalNameFromCertificate(userCertificate);
-        final String idCode = Objects.requireNonNull(CertificateData.getSubjectIdCode(userCertificate));
+        final String idCode = CertificateData.getSubjectIdCode(userCertificate)
+                .orElseThrow(() -> new CertificateEncodingException("Certificate does not contain subject ID code"));
         return new WebEidAuthentication(principalName, idCode, authorities);
     }
 
@@ -52,12 +54,15 @@ private WebEidAuthentication(String principalName, String idCode, List<GrantedAu
     }
 
     private static String getPrincipalNameFromCertificate(X509Certificate userCertificate) throws CertificateEncodingException {
-        try {
-            return Objects.requireNonNull(CertificateData.getSubjectGivenName(userCertificate)) + ' ' +
-                    Objects.requireNonNull(CertificateData.getSubjectSurname(userCertificate));
-        } catch (CertificateEncodingException e) {
+        final Optional<String> givenName = CertificateData.getSubjectGivenName(userCertificate);
+        final Optional<String> surname = CertificateData.getSubjectSurname(userCertificate);
+
+        if (givenName.isPresent() && surname.isPresent()) {
+            return givenName.get() + ' ' + surname.get();
+        } else {
             // Organization certificates do not have given name and surname fields.
-            return Objects.requireNonNull(CertificateData.getSubjectCN(userCertificate));
+            return CertificateData.getSubjectCN(userCertificate)
+                    .orElseThrow(() -> new CertificateEncodingException("Certificate does not contain subject CN"));
         }
     }
 
diff --git a/src/main/java/eu/webeid/example/service/SigningService.java b/src/main/java/eu/webeid/example/service/SigningService.java
index e96af33..507b4b3 100644
--- a/src/main/java/eu/webeid/example/service/SigningService.java
+++ b/src/main/java/eu/webeid/example/service/SigningService.java
@@ -90,15 +90,17 @@ private HttpSession currentSession() {
      * @return data to be signed
      */
     public DigestDTO prepareContainer(CertificateDTO certificateDTO, WebEidAuthentication authentication) throws CertificateException, NoSuchAlgorithmException, IOException {
-        X509Certificate certificate = certificateDTO.toX509Certificate();
-        if (!authentication.getIdCode().equals(CertificateData.getSubjectIdCode(certificate))) {
+        final X509Certificate certificate = certificateDTO.toX509Certificate();
+        final String signingIdCode = CertificateData.getSubjectIdCode(certificate)
+                .orElseThrow(() -> new RuntimeException("Certificate does not contain subject ID code"));
+        if (!signingIdCode.equals(authentication.getIdCode())) {
             throw new IllegalArgumentException("Authenticated subject ID code differs from " +
                     "signing certificate subject ID code");
         }
 
-        FileDTO fileDTO = FileDTO.getExampleForSigningFromResources();
-        Container containerToSign = getContainerToSign(fileDTO);
-        String containerName = generateContainerName(fileDTO.getName());
+        final FileDTO fileDTO = FileDTO.getExampleForSigningFromResources();
+        final Container containerToSign = getContainerToSign(fileDTO);
+        final String containerName = generateContainerName(fileDTO.getName());
 
         currentSession().setAttribute(SESSION_ATTR_CONTAINER, containerToSign);
         currentSession().setAttribute(SESSION_ATTR_FILE, fileDTO);
@@ -113,7 +115,7 @@ public DigestDTO prepareContainer(CertificateDTO certificateDTO, WebEidAuthentic
                     "' is not supported. Supported algorithms are: " + String.join(", ", certificateDTO.getSupportedHashFunctionNames()));
         }
 
-        DataToSign dataToSign = SignatureBuilder
+        final DataToSign dataToSign = SignatureBuilder
                 .aSignature(containerToSign)
                 .withSignatureProfile(SignatureProfile.LT) // AIA OCSP is supported for signatures with LT or LTA profile.
                 .withSigningCertificate(certificate)
@@ -127,7 +129,7 @@ public DigestDTO prepareContainer(CertificateDTO certificateDTO, WebEidAuthentic
         final byte[] digest = signatureDigestAlgorithm.getDssDigestAlgorithm().getMessageDigest()
                 .digest(dataToSign.getDataToSign());
 
-        DigestDTO digestDTO = new DigestDTO();
+        final DigestDTO digestDTO = new DigestDTO();
         digestDTO.setHash(DatatypeConverter.printBase64Binary(digest));
         digestDTO.setHashFunction(digestAlgorithmName);