diff --git a/sdk/pom.xml b/sdk/pom.xml
index 64497996..859f975a 100644
--- a/sdk/pom.xml
+++ b/sdk/pom.xml
@@ -18,6 +18,22 @@
         <okhttp.version>4.12.0</okhttp.version>
         <platform.branch>protocol/go/v0.16.0</platform.branch>
     </properties>
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.junit.platform</groupId>
+                <artifactId>junit-platform-commons</artifactId>
+                <version>1.11.0</version>
+                <scope>test</scope>
+            </dependency>
+            <dependency>
+                <groupId>org.junit.platform</groupId>
+                <artifactId>junit-platform-engine</artifactId>
+                <version>1.11.0</version>
+                <scope>test</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
     <dependencies>
         <!-- Logging Dependencies -->
         <dependency>
@@ -289,6 +305,12 @@
             <version>${kotlin.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.tngtech.archunit</groupId>
+            <artifactId>archunit-junit5</artifactId>
+            <version>1.3.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
     <build>
         <resources>
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/AesGcm.java b/sdk/src/main/java/io/opentdf/platform/sdk/AesGcm.java
index 71445f69..f5bb0bee 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/AesGcm.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/AesGcm.java
@@ -17,7 +17,7 @@
  * It includes methods to encrypt and decrypt byte arrays using a specified
  * symmetric key.
  */
-public class AesGcm {
+class AesGcm {
     public static final int GCM_NONCE_LENGTH = 12; // in bytes
     public static final int GCM_TAG_LENGTH = 16; // in bytes
     private static final String CIPHER_TRANSFORM = "AES/GCM/NoPadding";
@@ -34,7 +34,7 @@ public byte[] getKey() {
         return key.getEncoded();
     }
 
-    public static class Encrypted {
+    static class Encrypted {
         private final byte[] iv;
         private final byte[] ciphertext;
 
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/AssertionConfig.java b/sdk/src/main/java/io/opentdf/platform/sdk/AssertionConfig.java
index a1e83a8d..8a79fe6a 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/AssertionConfig.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/AssertionConfig.java
@@ -73,7 +73,7 @@ public String toString() {
         }
     }
 
-    public enum BindingMethod {
+    enum BindingMethod {
         JWS("jws");
 
         private String method;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/AsymDecryption.java b/sdk/src/main/java/io/opentdf/platform/sdk/AsymDecryption.java
index b76d1523..671201fe 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/AsymDecryption.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/AsymDecryption.java
@@ -12,7 +12,7 @@
 /**
  * Class providing functionality for asymmetric decryption using an RSA private key.
  */
-public class AsymDecryption {
+class AsymDecryption {
     private final PrivateKey privateKey;
     private static final String PRIVATE_KEY_HEADER = "-----BEGIN PRIVATE KEY-----";
     private static final String PRIVATE_KEY_FOOTER = "-----END PRIVATE KEY-----";
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/AsymEncryption.java b/sdk/src/main/java/io/opentdf/platform/sdk/AsymEncryption.java
index 3a81b1f5..fd81bda4 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/AsymEncryption.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/AsymEncryption.java
@@ -19,7 +19,7 @@
  * AsymEncryption class provides methods for asymmetric encryption and
  * handling public keys in PEM format.
  */
-public class AsymEncryption {
+class AsymEncryption {
     private final PublicKey publicKey;
     private static final String PUBLIC_KEY_HEADER = "-----BEGIN PUBLIC KEY-----";
     private static final String PUBLIC_KEY_FOOTER = "-----END PUBLIC KEY-----";
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/Autoconfigure.java b/sdk/src/main/java/io/opentdf/platform/sdk/Autoconfigure.java
index ffe9e239..520ecdf5 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/Autoconfigure.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/Autoconfigure.java
@@ -54,7 +54,7 @@ class RuleType {
  * This class includes functionality to create granter instances based on
  * attributes either from a list of attribute values or from a service.
  */
-public class Autoconfigure {
+class Autoconfigure {
 
     private static Logger logger = LoggerFactory.getLogger(Autoconfigure.class);
 
@@ -98,7 +98,7 @@ public KeySplitTemplate(String kas, String splitID, String kid, KeyType keyType)
         }
     }
 
-    public static class KeySplitStep {
+    static class KeySplitStep {
         final String kas;
         final String splitID;
 
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/CryptoUtils.java b/sdk/src/main/java/io/opentdf/platform/sdk/CryptoUtils.java
index 158e47be..e9c35cd5 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/CryptoUtils.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/CryptoUtils.java
@@ -12,7 +12,7 @@
 /**
  * Utility class for cryptographic operations such as generating RSA key pairs and calculating HMAC.
  */
-public class CryptoUtils {
+class CryptoUtils {
     private static final int KEYPAIR_SIZE = 2048;
 
     public static byte[] CalculateSHA256Hmac(byte[] key, byte[] data) {
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/ECCurve.java b/sdk/src/main/java/io/opentdf/platform/sdk/ECCurve.java
index 79edbec0..2c1a6173 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/ECCurve.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/ECCurve.java
@@ -10,7 +10,7 @@
 /**
  * Elliptic curve definitions for EC key operations.
  */
-public enum ECCurve {
+enum ECCurve {
     SECP256R1("secp256r1", 32, 33, 0x00),
     SECP384R1("secp384r1", 48, 49, 0x01),
     SECP521R1("secp521r1", 66, 67, 0x02),
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/ECKeyPair.java b/sdk/src/main/java/io/opentdf/platform/sdk/ECKeyPair.java
index 36110853..a4279a70 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/ECKeyPair.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/ECKeyPair.java
@@ -27,7 +27,7 @@
 import java.util.Objects;
 // https://www.bouncycastle.org/latest_releases.html
 
-public class ECKeyPair {
+class ECKeyPair {
 
     private static final int SHA256_BYTES = 32;
 
@@ -37,7 +37,7 @@ public class ECKeyPair {
 
     private final ECCurve curve;
 
-    public enum ECAlgorithm {
+    enum ECAlgorithm {
         ECDH,
         ECDSA
     }
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/EntityIdentifiers.java b/sdk/src/main/java/io/opentdf/platform/sdk/EntityIdentifiers.java
index af6e4234..764f84f4 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/EntityIdentifiers.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/EntityIdentifiers.java
@@ -27,7 +27,7 @@
  * EntityIdentifiers.forEmail("jen@example.com");
  * }</pre>
  */
-public final class EntityIdentifiers {
+final class EntityIdentifiers {
 
     private EntityIdentifiers() {}
 
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/InvalidZipException.java b/sdk/src/main/java/io/opentdf/platform/sdk/InvalidZipException.java
index 8bba58bd..4a7d33f0 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/InvalidZipException.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/InvalidZipException.java
@@ -5,7 +5,7 @@
  * is invalid or corrupted in some way. This exception extends RuntimeException,
  * allowing it to be thrown during the normal operation of the Java Virtual Machine.
  */
-public class InvalidZipException extends RuntimeException {
+public class InvalidZipException extends SDKException {
     public InvalidZipException(String message) {
         super(message);
     }
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/Manifest.java b/sdk/src/main/java/io/opentdf/platform/sdk/Manifest.java
index 20fbb13e..eb802c4e 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/Manifest.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/Manifest.java
@@ -96,7 +96,7 @@ public JsonElement serialize(Object src, Type typeOfSrc, JsonSerializationContex
         }
     }
 
-    static public class Segment {
+    static class Segment {
         public String hash;
         public long segmentSize;
         public long encryptedSegmentSize;
@@ -167,7 +167,7 @@ public int hashCode() {
         }
     }
 
-    static public class PolicyBinding {
+    static class PolicyBinding {
         public String alg;
         public String hash;
 
@@ -298,7 +298,7 @@ public int hashCode() {
         }
     }
 
-    static public class Binding {
+    static class Binding {
         public String method;
         public String signature;
 
@@ -318,14 +318,14 @@ public int hashCode() {
         }
     }
 
-    static public class Assertion {
+    static class Assertion {
         public String id;
         public String type;
         public String scope;
         public String appliesToState;
         public AssertionConfig.Statement statement;
         public Binding binding;
-        static public class HashValues {
+        static class HashValues {
             private final String assertionHash;
             private final String signature;
 
@@ -528,7 +528,7 @@ private JWSVerifier createVerifier(RSAPublicKey publicKey) {
         }
     }
 
-    public static class AssertionValueAdapter implements JsonDeserializer<AssertionConfig.Statement> {
+    static class AssertionValueAdapter implements JsonDeserializer<AssertionConfig.Statement> {
         @Override
         public AssertionConfig.Statement deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
             if (!json.isJsonObject()) {
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/Planner.java b/sdk/src/main/java/io/opentdf/platform/sdk/Planner.java
index 477d315a..00e2ec1a 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/Planner.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/Planner.java
@@ -25,7 +25,7 @@
 import java.util.stream.Collectors;
 
 
-public class Planner {
+class Planner {
     private static final String BASE_KEY = "base_key";
     private final Config.TDFConfig tdfConfig;
     private final SDK.Services services;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/PolicyEnums.java b/sdk/src/main/java/io/opentdf/platform/sdk/PolicyEnums.java
index 5c426cf8..d6aee7b6 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/PolicyEnums.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/PolicyEnums.java
@@ -22,7 +22,7 @@
  *     .setOperator(OPERATOR_IN);
  * }</pre>
  */
-public final class PolicyEnums {
+final class PolicyEnums {
 
     private PolicyEnums() {}
 
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/PolicyObject.java b/sdk/src/main/java/io/opentdf/platform/sdk/PolicyObject.java
index 9d708699..bd9a18f3 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/PolicyObject.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/PolicyObject.java
@@ -6,7 +6,7 @@
  * The PolicyObject class represents a policy with a unique identifier and a body containing data attributes.
  */
 public class PolicyObject {
-    static public class AttributeObject {
+    static class AttributeObject {
         public String attribute;
         public String displayName;
         public boolean isDefault;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/Resources.java b/sdk/src/main/java/io/opentdf/platform/sdk/Resources.java
index 527bec7f..e83546d8 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/Resources.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/Resources.java
@@ -24,7 +24,7 @@
  * Resources.forAttributeValues("https://example.com/attr/department/value/finance");
  * }</pre>
  */
-public final class Resources {
+final class Resources {
 
     private Resources() {}
 
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/TDFReader.java b/sdk/src/main/java/io/opentdf/platform/sdk/TDFReader.java
index 6e9f32d2..b94844d2 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/TDFReader.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/TDFReader.java
@@ -16,7 +16,7 @@
  * The class initializes with a TDF file channel, extracts the manifest and payload entries,
  * and provides methods to retrieve the manifest content, read payload bytes, and read policy objects.
  */
-public class TDFReader {
+class TDFReader {
 
     private final ZipReader.Entry manifestEntry;
     private final InputStream payload;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/TDFWriter.java b/sdk/src/main/java/io/opentdf/platform/sdk/TDFWriter.java
index 048822f6..825f51db 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/TDFWriter.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/TDFWriter.java
@@ -8,7 +8,7 @@
  * The TDFWriter class provides functionalities for creating a TDF (Trusted Data Format) archive.
  * This includes appending a manifest file and appending payload data to the archive.
  */
-public class TDFWriter {
+class TDFWriter {
     public static final String TDF_PAYLOAD_FILE_NAME = "0.payload";
     public static final String TDF_MANIFEST_FILE_NAME = "0.manifest.json";
     private final ZipWriter archiveWriter;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/ZipReader.java b/sdk/src/main/java/io/opentdf/platform/sdk/ZipReader.java
index cf0b5772..2a3578d9 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/ZipReader.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/ZipReader.java
@@ -19,7 +19,7 @@
  * Local File Header. This class supports standard ZIP archives as well
  * as ZIP64 format.
  */
-public class ZipReader {
+class ZipReader {
 
     public static final Logger logger = LoggerFactory.getLogger(ZipReader.class);
     public static final int END_OF_CENTRAL_DIRECTORY_SIZE = 22;
@@ -148,7 +148,7 @@ private CentralDirectoryRecord extractZIP64CentralDirectoryInfo() throws IOExcep
         return new CentralDirectoryRecord(totalNumCDEntries, cdOffset);
     }
 
-    public class Entry {
+    class Entry {
         private final long fileSize;
         private final String fileName;
         final long offsetToLocalHeader;
diff --git a/sdk/src/main/java/io/opentdf/platform/sdk/ZipWriter.java b/sdk/src/main/java/io/opentdf/platform/sdk/ZipWriter.java
index 71aea34c..862e14a4 100644
--- a/sdk/src/main/java/io/opentdf/platform/sdk/ZipWriter.java
+++ b/sdk/src/main/java/io/opentdf/platform/sdk/ZipWriter.java
@@ -13,7 +13,7 @@
  * The ZipWriter class provides functionalities to create ZIP archive files.
  * It writes files and data to an underlying output stream in the ZIP file format.
  */
-public class ZipWriter {
+class ZipWriter {
 
     private static final int ZIP_VERSION = 0x2D;
     private static final int ZIP_64_MAGIC_VAL = 0xFFFFFFFF;
diff --git a/sdk/src/test/java/io/opentdf/platform/sdk/Fuzzing.java b/sdk/src/test/java/io/opentdf/platform/sdk/Fuzzing.java
index 72ce61d0..eda53fee 100644
--- a/sdk/src/test/java/io/opentdf/platform/sdk/Fuzzing.java
+++ b/sdk/src/test/java/io/opentdf/platform/sdk/Fuzzing.java
@@ -39,7 +39,7 @@ public void fuzzTDF(FuzzedDataProvider data) {
             Reader reader = tdf.loadTDF(new SeekableInMemoryByteChannel(fuzzBytes), readerConfig);
 
             reader.readPayload(IGNORE_OUTPUT_STREAM);
-        } catch (SDKException | InvalidZipException | JsonParseException | IOException | IllegalArgumentException e) {
+        } catch (SDKException | JsonParseException | IOException | IllegalArgumentException e) {
             // expected failure cases
         }
     }