diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4532094..be93a9d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,9 +5,6 @@ SPDX-License-Identifier: CC0-1.0
 
 # Cert-D-Java Changelog
 
-## 0.2.2
-- Bump Bouncy Castle to `1.75`
-
 ## 0.2.1
 - Throw `NoSuchElementException` when querying non-existent certificates
 
diff --git a/pgp-cert-d-java/build.gradle b/pgp-cert-d-java/build.gradle
index 19f1329..d59867d 100644
--- a/pgp-cert-d-java/build.gradle
+++ b/pgp-cert-d-java/build.gradle
@@ -32,7 +32,7 @@ dependencies {
     testImplementation project(":pgp-cert-d-java-jdbc-sqlite-lookup")
 
     testImplementation "org.bouncycastle:bcprov-jdk15to18:$bouncycastleVersion"
-    testImplementation "org.bouncycastle:bcpg-jdk15to18:$bouncyPgVersion"
+    testImplementation "org.bouncycastle:bcpg-jdk15to18:$bouncycastleVersion"
 }
 
 animalsniffer {
diff --git a/pgp-cert-d-java/src/main/java/pgp/cert_d/ReadOnlyPGPCertificateDirectory.java b/pgp-cert-d-java/src/main/java/pgp/cert_d/ReadOnlyPGPCertificateDirectory.java
index 1b27ffb..0b1416c 100644
--- a/pgp-cert-d-java/src/main/java/pgp/cert_d/ReadOnlyPGPCertificateDirectory.java
+++ b/pgp-cert-d-java/src/main/java/pgp/cert_d/ReadOnlyPGPCertificateDirectory.java
@@ -10,7 +10,6 @@ import pgp.certificate_store.exception.BadNameException;
 
 import java.io.IOException;
 import java.util.Iterator;
-import java.util.NoSuchElementException;
 
 /**
  * Interface for a read-only OpenPGP certificate directory.
@@ -20,12 +19,12 @@ public interface ReadOnlyPGPCertificateDirectory {
     /**
      * Get the trust-root certificate. This is a certificate which is stored under the special name
      * <pre>trust-root</pre>.
+     * If no such certificate is found, <pre>null</pre> is returned.
      *
      * @return trust-root certificate
      *
      * @throws IOException in case of an IO error
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getTrustRootCertificate()
             throws IOException, BadDataException;
@@ -37,25 +36,24 @@ public interface ReadOnlyPGPCertificateDirectory {
      * Otherwise. the changed certificate is returned.
      *
      * @param tag tag
-     * @return changed certificate, or null if the certificate is unchanged.
+     * @return changed certificate, or null if the certificate is unchanged or not found.
      *
      * @throws IOException in case of an IO error
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getTrustRootCertificateIfChanged(long tag)
             throws IOException, BadDataException;
 
     /**
      * Get the certificate identified by the given fingerprint.
+     * If no such certificate is found, return <pre>null</pre>.
      *
      * @param fingerprint lower-case fingerprint of the certificate
-     * @return certificate
+     * @return certificate or null if no such certificate has been found
      *
      * @throws IOException in case of an IO error
      * @throws BadNameException if the fingerprint is malformed
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getByFingerprint(String fingerprint)
             throws IOException, BadNameException, BadDataException;
@@ -68,26 +66,25 @@ public interface ReadOnlyPGPCertificateDirectory {
      *
      * @param fingerprint lower-case fingerprint of the certificate
      * @param tag tag
-     * @return certificate or null if the certificate has not been changed
+     * @return certificate or null if the certificate has not been changed or has not been found
      *
      * @throws IOException in case of an IO error
      * @throws BadNameException if the fingerprint is malformed
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getByFingerprintIfChanged(String fingerprint, long tag)
             throws IOException, BadNameException, BadDataException;
 
     /**
      * Get the certificate identified by the given special name.
+     * If no such certificate is found, <pre>null</pre> is returned.
      *
      * @param specialName special name
-     * @return certificate
+     * @return certificate or null
      *
      * @throws IOException in case of an IO error
      * @throws BadNameException if the special name is not known
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getBySpecialName(String specialName)
             throws IOException, BadNameException, BadDataException;
@@ -105,7 +102,6 @@ public interface ReadOnlyPGPCertificateDirectory {
      * @throws IOException in case of an IO error
      * @throws BadNameException if the special name is not known
      * @throws BadDataException if the certificate contains bad data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getBySpecialNameIfChanged(String specialName, long tag)
             throws IOException, BadNameException, BadDataException;
diff --git a/pgp-cert-d-java/src/test/java/pgp/cert_d/BaseDirectoryProviderTest.java b/pgp-cert-d-java/src/test/java/pgp/cert_d/BaseDirectoryProviderTest.java
index f6af1be..357ba3f 100644
--- a/pgp-cert-d-java/src/test/java/pgp/cert_d/BaseDirectoryProviderTest.java
+++ b/pgp-cert-d-java/src/test/java/pgp/cert_d/BaseDirectoryProviderTest.java
@@ -18,7 +18,7 @@ public class BaseDirectoryProviderTest {
     public void testGetDefaultBaseDir_Linux() {
         assumeTrue(System.getProperty("os.name").equalsIgnoreCase("linux"));
         File baseDir = BaseDirectoryProvider.getDefaultBaseDirForOS("linux");
-        assertTrue(baseDir.getAbsolutePath().endsWith("pgp.cert.d"));
+        assertTrue(baseDir.getAbsolutePath().endsWith("/.local/share/pgp.cert.d"));
     }
 
     @Test
diff --git a/pgp-certificate-store/src/main/java/pgp/certificate_store/PGPCertificateStore.java b/pgp-certificate-store/src/main/java/pgp/certificate_store/PGPCertificateStore.java
index 251229f..d0915b0 100644
--- a/pgp-certificate-store/src/main/java/pgp/certificate_store/PGPCertificateStore.java
+++ b/pgp-certificate-store/src/main/java/pgp/certificate_store/PGPCertificateStore.java
@@ -12,7 +12,6 @@ import pgp.certificate_store.exception.BadNameException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Iterator;
-import java.util.NoSuchElementException;
 
 /**
  * Interface for an OpenPGP certificate (public key) store.
@@ -21,6 +20,7 @@ public interface PGPCertificateStore {
 
     /**
      * Return the certificate that matches the given identifier.
+     * If no matching certificate can be found, return null.
      *
      * @param identifier identifier for a certificate.
      * @return certificate or null
@@ -28,7 +28,6 @@ public interface PGPCertificateStore {
      * @throws IOException in case of an IO-error
      * @throws BadNameException if the identifier is invalid
      * @throws BadDataException if the certificate file contains invalid data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getCertificate(String identifier)
             throws IOException, BadNameException, BadDataException;
@@ -46,7 +45,6 @@ public interface PGPCertificateStore {
      * @throws IOException in case of an IO-error
      * @throws BadNameException if the identifier is invalid
      * @throws BadDataException if the certificate file contains invalid data
-     * @throws NoSuchElementException if no such certificate is found
      */
     Certificate getCertificateIfChanged(String identifier, Long tag)
             throws IOException, BadNameException, BadDataException;
diff --git a/version.gradle b/version.gradle
index 2903026..ce74cbd 100644
--- a/version.gradle
+++ b/version.gradle
@@ -4,16 +4,15 @@
 
 allprojects {
     ext {
-        shortVersion = '0.2.3'
+        shortVersion = '0.2.2'
         isSnapshot = true
         minAndroidSdk = 26
         animalsnifferSignatureVersion = "$minAndroidSdk:8.0.0_r2"
         javaSourceCompatibility = 1.8
-        bouncycastleVersion = '1.75'
-        bouncyPgVersion = "$bouncycastleVersion"
+        bouncycastleVersion = '1.71'
         slf4jVersion = '1.7.36'
         logbackVersion = '1.2.11'
         junitVersion = '5.8.2'
-        sqliteJdbcVersion = '3.42.0.0'
+        sqliteJdbcVersion = '3.36.0.3'
     }
 }