diff --git a/external-sop/build.gradle b/external-sop/build.gradle
index 83bfe3c..87b8e04 100644
--- a/external-sop/build.gradle
+++ b/external-sop/build.gradle
@@ -23,6 +23,9 @@ dependencies {
 
     // Compare version strings
     implementation 'org.apache.maven:maven-artifact:3.6.3'
+    
+    // @Nonnull, @Nullable...
+    implementation "com.google.code.findbugs:jsr305:$jsrVersion"
 }
 
 test {
diff --git a/external-sop/src/main/java/sop/external/ExternalSOP.java b/external-sop/src/main/java/sop/external/ExternalSOP.java
index b4763c6..c2ec911 100644
--- a/external-sop/src/main/java/sop/external/ExternalSOP.java
+++ b/external-sop/src/main/java/sop/external/ExternalSOP.java
@@ -33,9 +33,11 @@ import sop.operation.InlineVerify;
 import sop.operation.Version;
 
 import java.io.ByteArrayOutputStream;
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Properties;
@@ -44,14 +46,24 @@ public class ExternalSOP implements SOP {
 
     private final String binaryName;
     private final Properties properties;
+    private final TempDirProvider tempDirProvider;
 
     public ExternalSOP(String binaryName) {
         this(binaryName, new Properties());
     }
 
     public ExternalSOP(String binaryName, Properties properties) {
+        this(binaryName, properties, defaultTempDirProvider());
+    }
+
+    public ExternalSOP(String binaryName, TempDirProvider tempDirProvider) {
+        this(binaryName, new Properties(), tempDirProvider);
+    }
+
+    public ExternalSOP(String binaryName, Properties properties, TempDirProvider tempDirProvider) {
         this.binaryName = binaryName;
         this.properties = properties;
+        this.tempDirProvider = tempDirProvider;
     }
 
     @Override
@@ -101,7 +113,7 @@ public class ExternalSOP implements SOP {
 
     @Override
     public Decrypt decrypt() {
-        return new DecryptExternal(binaryName, properties);
+        return new DecryptExternal(binaryName, properties, tempDirProvider);
     }
 
     @Override
@@ -303,4 +315,17 @@ public class ExternalSOP implements SOP {
             throw new RuntimeException(e);
         }
     }
+
+    public interface TempDirProvider {
+        File provideTempDirectory() throws IOException;
+    }
+
+    public static TempDirProvider defaultTempDirProvider() {
+        return new TempDirProvider() {
+            @Override
+            public File provideTempDirectory() throws IOException {
+                return Files.createTempDirectory("ext-sop").toFile();
+            }
+        };
+    }
 }
diff --git a/external-sop/src/main/java/sop/external/operation/DecryptExternal.java b/external-sop/src/main/java/sop/external/operation/DecryptExternal.java
index 9373bcd..f6b2b7f 100644
--- a/external-sop/src/main/java/sop/external/operation/DecryptExternal.java
+++ b/external-sop/src/main/java/sop/external/operation/DecryptExternal.java
@@ -12,6 +12,7 @@ import sop.external.ExternalSOP;
 import sop.operation.Decrypt;
 import sop.util.UTCUtil;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -23,6 +24,7 @@ import java.util.Properties;
 
 public class DecryptExternal implements Decrypt {
 
+    private final ExternalSOP.TempDirProvider tempDirProvider;
     private final List<String> commandList = new ArrayList<>();
     private final List<String> envList;
 
@@ -32,7 +34,8 @@ public class DecryptExternal implements Decrypt {
     private int keyCounter = 0;
     private int withKeyPasswordCounter = 0;
 
-    public DecryptExternal(String binary, Properties environment) {
+    public DecryptExternal(String binary, Properties environment, ExternalSOP.TempDirProvider tempDirProvider) {
+        this.tempDirProvider = tempDirProvider;
         this.commandList.add(binary);
         this.commandList.add("decrypt");
         this.envList = ExternalSOP.propertiesToEnv(environment);
@@ -41,14 +44,14 @@ public class DecryptExternal implements Decrypt {
     @Override
     public Decrypt verifyNotBefore(Date timestamp)
             throws SOPGPException.UnsupportedOption {
-        this.commandList.add("--not-before=" + UTCUtil.formatUTCDate(timestamp));
+        this.commandList.add("--verify-not-before=" + UTCUtil.formatUTCDate(timestamp));
         return this;
     }
 
     @Override
     public Decrypt verifyNotAfter(Date timestamp)
             throws SOPGPException.UnsupportedOption {
-        this.commandList.add("--not-after=" + UTCUtil.formatUTCDate(timestamp));
+        this.commandList.add("--verify-not-after=" + UTCUtil.formatUTCDate(timestamp));
         return this;
     }
 
@@ -101,6 +104,14 @@ public class DecryptExternal implements Decrypt {
     public ReadyWithResult<DecryptionResult> ciphertext(InputStream ciphertext)
             throws SOPGPException.BadData, SOPGPException.MissingArg, SOPGPException.CannotDecrypt,
             SOPGPException.KeyIsProtected, IOException {
+
+        File tempDir = tempDirProvider.provideTempDirectory();
+        File sessionKeyOut = new File(tempDir, "session-key-out");
+        commandList.add("--session-key-out=" + sessionKeyOut.getAbsolutePath());
+
+        File verifyOut = new File(tempDir, "verify-out");
+        commandList.add("--verify-out=" + verifyOut.getAbsolutePath());
+
         String[] command = commandList.toArray(new String[0]);
         String[] env = envList.toArray(new String[0]);
         try {
diff --git a/sop-java/src/main/java/sop/exception/SOPGPException.java b/sop-java/src/main/java/sop/exception/SOPGPException.java
index 71c14a7..7d15705 100644
--- a/sop-java/src/main/java/sop/exception/SOPGPException.java
+++ b/sop-java/src/main/java/sop/exception/SOPGPException.java
@@ -94,7 +94,7 @@ public abstract class SOPGPException extends RuntimeException {
         public static final int EXIT_CODE = 19;
 
         public MissingArg() {
-            
+
         }
 
         public MissingArg(String message) {