src/main/java/org/apache/sysds/runtime/privacy/PrivacyPropagator.java - systemds - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing,
  * software distributed under the License is distributed on an
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied.  See the License for the
  * specific language governing permissions and limitations
  * under the License.
  */

 package org.apache.sysds.runtime.privacy;

 import java.util.function.Function;

 import org.apache.sysds.parser.DataExpression;
 import org.apache.sysds.runtime.controlprogram.caching.CacheableData;
 import org.apache.sysds.runtime.controlprogram.context.ExecutionContext;
 import org.apache.sysds.runtime.instructions.Instruction;
 import org.apache.sysds.runtime.instructions.cp.BinaryCPInstruction;
 import org.apache.sysds.runtime.instructions.cp.BuiltinNaryCPInstruction;
 import org.apache.sysds.runtime.instructions.cp.CPInstruction;
 import org.apache.sysds.runtime.instructions.cp.CPOperand;
 import org.apache.sysds.runtime.instructions.cp.ComputationCPInstruction;
 import org.apache.sysds.runtime.instructions.cp.Data;
 import org.apache.sysds.runtime.instructions.cp.QuaternaryCPInstruction;
 import org.apache.sysds.runtime.instructions.cp.UnaryCPInstruction;
 import org.apache.sysds.runtime.instructions.cp.VariableCPInstruction;
 import org.apache.sysds.runtime.privacy.PrivacyConstraint.PrivacyLevel;
 import org.apache.wink.json4j.JSONException;
 import org.apache.wink.json4j.JSONObject;

 /**
  * Class with static methods merging privacy constraints of operands
  * in expressions to generate the privacy constraints of the output.
  */
 public class PrivacyPropagator
 {
 	public static CacheableData<?> parseAndSetPrivacyConstraint(CacheableData<?> cd, JSONObject mtd)
 		throws JSONException
 	{
 		if ( mtd.containsKey(DataExpression.PRIVACY) ) {
 			String privacyLevel = mtd.getString(DataExpression.PRIVACY);
 			if ( privacyLevel != null )
 				cd.setPrivacyConstraints(new PrivacyConstraint(PrivacyLevel.valueOf(privacyLevel)));
 		}
 		return cd;
 	}

 	public static PrivacyConstraint mergeBinary(PrivacyConstraint privacyConstraint1, PrivacyConstraint privacyConstraint2) {
 		if (privacyConstraint1 != null && privacyConstraint2 != null){
 			PrivacyLevel privacyLevel1 = privacyConstraint1.getPrivacyLevel();
 			PrivacyLevel privacyLevel2 = privacyConstraint2.getPrivacyLevel();

 			// One of the inputs are private, hence the output must be private.
 			if (privacyLevel1 == PrivacyLevel.Private || privacyLevel2 == PrivacyLevel.Private)
 				return new PrivacyConstraint(PrivacyLevel.Private);
 			// One of the inputs are private with aggregation allowed, but none of the inputs are completely private,
 			// hence the output must be private with aggregation.
 			else if (privacyLevel1 == PrivacyLevel.PrivateAggregation || privacyLevel2 == PrivacyLevel.PrivateAggregation)
 				return new PrivacyConstraint(PrivacyLevel.PrivateAggregation);
 			// Both inputs have privacy level "None", hence the privacy constraint can be removed.
 			else
 				return null;
 		}
 		else if (privacyConstraint1 != null)
 			return privacyConstraint1;
 		else if (privacyConstraint2 != null)
 			return privacyConstraint2;
 		return null;
 	}

 	public static PrivacyConstraint mergeTernary(PrivacyConstraint[] privacyConstraints){
 		return mergeBinary(mergeBinary(privacyConstraints[0], privacyConstraints[1]), privacyConstraints[2]);
 	}

 	public static PrivacyConstraint mergeQuaternary(PrivacyConstraint[] privacyConstraints){
 		return mergeBinary(mergeTernary(privacyConstraints), privacyConstraints[3]);
 	}

 	public static PrivacyConstraint mergeNary(PrivacyConstraint[] privacyConstraints){
 		PrivacyConstraint mergedPrivacyConstraint = privacyConstraints[0];
 		for ( int i = 1; i < privacyConstraints.length; i++ ){
 			mergedPrivacyConstraint = mergeBinary(mergedPrivacyConstraint, privacyConstraints[i]);
 		}
 		return mergedPrivacyConstraint;
 	}

 	public static Instruction preprocessInstruction(Instruction inst, ExecutionContext ec){
 		switch ( inst.getType() ){
 			case CONTROL_PROGRAM:
 				return preprocessCPInstruction( (CPInstruction) inst, ec );
 			case BREAKPOINT:
 			case SPARK:
 			case GPU:
 			case FEDERATED:
 				return inst;
 			default:
 				throwExceptionIfPrivacyActivated(inst, ec);
 				return inst;
 		}
 	}

 	public static Instruction preprocessCPInstruction(CPInstruction inst, ExecutionContext ec){
 		switch ( inst.getCPInstructionType() )
 		{
 			case Variable:
 				return preprocessVariableCPInstruction((VariableCPInstruction) inst, ec);
 			case AggregateUnary:
 			case Reorg:
 			case Unary:
 				return preprocessUnaryCPInstruction((UnaryCPInstruction) inst, ec);
 			case AggregateBinary:
 			case Append:
 			case Binary:
 				return preprocessBinaryCPInstruction((BinaryCPInstruction) inst, ec);
 			case AggregateTernary:
 			case Ternary:
 				return preprocessTernaryCPInstruction((ComputationCPInstruction) inst, ec);
 			case Quaternary:
 				return preprocessQuaternary((QuaternaryCPInstruction) inst, ec);
 			case BuiltinNary:
 			case Builtin:
 				return preprocessBuiltinNary((BuiltinNaryCPInstruction) inst, ec);
 			case Ctable:
 			case MultiReturnParameterizedBuiltin:
 			case MultiReturnBuiltin:
 			case ParameterizedBuiltin:
 			default:
 				return preprocessInstructionSimple(inst, ec);
 		}
 	}

 	/**
 	 * Throw exception if privacy constraints are activated or return instruction if privacy is not activated
 	 * @param inst instruction
 	 * @param ec execution context
 	 * @return instruction
 	 */
 	public static Instruction preprocessInstructionSimple(Instruction inst, ExecutionContext ec){
 		throwExceptionIfPrivacyActivated(inst, ec);
 		return inst;
 	}

 	public static Instruction preprocessBuiltinNary(BuiltinNaryCPInstruction inst, ExecutionContext ec){
 		if (inst.getInputs() == null) return inst;
 		PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, inst.getInputs());
 		PrivacyConstraint mergedPrivacyConstraint = mergeNary(privacyConstraints);
 		inst.setPrivacyConstraint(mergedPrivacyConstraint);
 		setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.getOutput());
 		return inst;
 	}

 	public static Instruction preprocessQuaternary(QuaternaryCPInstruction inst, ExecutionContext ec){
 		PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec,
 			new CPOperand[] {inst.input1,inst.input2,inst.input3,inst.getInput4()});
 		PrivacyConstraint mergedPrivacyConstraint = mergeQuaternary(privacyConstraints);
 		inst.setPrivacyConstraint(mergedPrivacyConstraint);
 		setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
 		return inst;
 	}

 	public static Instruction preprocessTernaryCPInstruction(ComputationCPInstruction inst, ExecutionContext ec){
 		PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, new CPOperand[]{inst.input1, inst.input2, inst.input3});
 		PrivacyConstraint mergedPrivacyConstraint = mergeTernary(privacyConstraints);
 		inst.setPrivacyConstraint(mergedPrivacyConstraint);
 		setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
 		return inst;
 	}

 	public static Instruction preprocessNaryInstruction(CPInstruction inst, ExecutionContext ec, CPOperand[] inputs, CPOperand output, Function<PrivacyConstraint[], PrivacyConstraint> mergeFunction){
 		PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, inputs);
 		PrivacyConstraint mergedPrivacyConstraint = mergeFunction.apply(privacyConstraints);
 		inst.setPrivacyConstraint(mergedPrivacyConstraint);
 		setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, output);
 		return inst;

 	}

 	public static Instruction preprocessBinaryCPInstruction(BinaryCPInstruction inst, ExecutionContext ec){
 		PrivacyConstraint privacyConstraint1 = getInputPrivacyConstraint(ec, inst.input1);
 		PrivacyConstraint privacyConstraint2 = getInputPrivacyConstraint(ec, inst.input2);
 		if ( privacyConstraint1 != null || privacyConstraint2 != null)
 		{
 			PrivacyConstraint mergedPrivacyConstraint = mergeBinary(privacyConstraint1, privacyConstraint2);
 			inst.setPrivacyConstraint(mergedPrivacyConstraint);
 			setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
 		}
 		return inst;
 	}

 	public static Instruction preprocessUnaryCPInstruction(UnaryCPInstruction inst, ExecutionContext ec){
 		return propagateInputPrivacy(inst, ec, inst.input1, inst.output);
 	}

 	public static Instruction preprocessVariableCPInstruction(VariableCPInstruction inst, ExecutionContext ec){
 		switch ( inst.getVariableOpcode() )
 		{
 			case CreateVariable:
 				return propagateSecondInputPrivacy(inst, ec);
 			case AssignVariable:
 				//Assigns scalar, hence it does not have privacy activated
 				return inst;
 			case CopyVariable:
 			case MoveVariable:
 				return propagateFirstInputPrivacy(inst, ec);
 			case RemoveVariable:
 				return propagateAllInputPrivacy(inst, ec);
 			case RemoveVariableAndFile:
 				return propagateFirstInputPrivacy(inst, ec);
 			case CastAsScalarVariable:
 				return propagateCastAsScalarVariablePrivacy(inst, ec);
 			case CastAsMatrixVariable:
 			case CastAsFrameVariable:
 				return propagateFirstInputPrivacy(inst, ec);
 			case CastAsDoubleVariable:
 			case CastAsIntegerVariable:
 			case CastAsBooleanVariable:
 				return propagateCastAsScalarVariablePrivacy(inst, ec);
 			case Read:
 				return inst;
 			case Write:
 				return propagateFirstInputPrivacy(inst, ec);
 			case SetFileName:
 				return propagateFirstInputPrivacy(inst, ec);
 			default:
 				throwExceptionIfPrivacyActivated(inst, ec);
 				return inst;
 		}
 	}

 	private static void throwExceptionIfPrivacyActivated(Instruction inst, ExecutionContext ec){
 		if ( inst.getPrivacyConstraint() != null && inst.getPrivacyConstraint().getPrivacyLevel().equals(PrivacyLevel.Private) ) {
 			throw new DMLPrivacyException("Instruction " + inst + " has privacy constraints activated, but the constraints are not propagated during preprocessing of instruction.");
 		}
 	}

 	/**
 	 * Propagate privacy from first input and throw exception if privacy is activated.
 	 * @param inst Instruction
 	 * @param ec execution context
 	 * @return instruction with or without privacy constraints
 	 */
 	private static Instruction propagateCastAsScalarVariablePrivacy(VariableCPInstruction inst, ExecutionContext ec){
 		inst = (VariableCPInstruction) propagateFirstInputPrivacy(inst, ec);
 		return preprocessInstructionSimple(inst, ec);
 	}

 	/**
 	 * Propagate privacy constraints from all inputs if privacy constraints are set.
 	 * @param inst instruction
 	 * @param ec execution context
 	 * @return instruction with or without privacy constraints
 	 */
 	private static Instruction propagateAllInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
 		//TODO: Propagate the most restricting constraints instead of just the latest activated constraint
 		for ( CPOperand input : inst.getInputs() )
 			inst = (VariableCPInstruction) propagateInputPrivacy(inst, ec, input, inst.getOutput());
 		return inst;
 	}

 	/**
 	 * Propagate privacy constraint to instruction and output of instruction
 	 * if data of first input is CacheableData and
 	 * privacy constraint is activated.
 	 * @param inst VariableCPInstruction
 	 * @param ec execution context
 	 * @return instruction with or without privacy constraints
 	 */
 	private static Instruction propagateFirstInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
 		return propagateInputPrivacy(inst, ec, inst.getInput1(), inst.getOutput());
 	}

 	/**
 	 * Propagate privacy constraint to instruction and output of instruction
 	 * if data of second input is CacheableData and
 	 * privacy constraint is activated.
 	 * @param inst VariableCPInstruction
 	 * @param ec execution context
 	 * @return instruction with or without privacy constraints
 	 */
 	private static Instruction propagateSecondInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
 		return propagateInputPrivacy(inst, ec, inst.getInput2(), inst.getOutput());
 	}

 	/**
 	 * Propagate privacy constraint to instruction and output of instruction
 	 * if data of the specified variable is CacheableData
 	 * and privacy constraint is activated
 	 * @param inst instruction
 	 * @param ec execution context
 	 * @param inputOperand input from which the privacy constraint is found
 	 * @param outputOperand output which the privacy constraint is propagated to
 	 * @return instruction with or without privacy constraints
 	 */
 	private static Instruction propagateInputPrivacy(Instruction inst, ExecutionContext ec, CPOperand inputOperand, CPOperand outputOperand){
 		PrivacyConstraint privacyConstraint = getInputPrivacyConstraint(ec, inputOperand);
 		if ( privacyConstraint != null ) {
 			inst.setPrivacyConstraint(privacyConstraint);
 			if ( outputOperand != null)
 				setOutputPrivacyConstraint(ec, privacyConstraint, outputOperand);
 		}
 		return inst;
 	}

 	private static PrivacyConstraint getInputPrivacyConstraint(ExecutionContext ec, CPOperand input){
 		if ( input != null && input.getName() != null){
 			Data dd = ec.getVariable(input.getName());
 			if ( dd != null && dd instanceof CacheableData)
 				return ((CacheableData<?>) dd).getPrivacyConstraint();
 		}
 		return null;
 	}


 	private static PrivacyConstraint[] getInputPrivacyConstraints(ExecutionContext ec, CPOperand[] inputs){
 		PrivacyConstraint[] privacyConstraints = new PrivacyConstraint[inputs.length];
 		for ( int i = 0; i < inputs.length; i++ ){
 			privacyConstraints[i] = getInputPrivacyConstraint(ec, inputs[i]);
 		}
 		return privacyConstraints;

 	}

 	private static void setOutputPrivacyConstraint(ExecutionContext ec, PrivacyConstraint privacyConstraint, CPOperand output){
 		Data dd = ec.getVariable(output.getName());
 		if ( dd != null ){
 			if ( dd instanceof CacheableData ){
 				((CacheableData<?>) dd).setPrivacyConstraints(privacyConstraint);
 				ec.setVariable(output.getName(), dd);
 			}
 			else throw new DMLPrivacyException("Privacy constraint of " + output + " cannot be set since it is not an instance of CacheableData");
 		}
 	}
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing,
	* software distributed under the License is distributed on an
	* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	* KIND, either express or implied. See the License for the
	* specific language governing permissions and limitations
	* under the License.
	*/

	package org.apache.sysds.runtime.privacy;

	import java.util.function.Function;

	import org.apache.sysds.parser.DataExpression;
	import org.apache.sysds.runtime.controlprogram.caching.CacheableData;
	import org.apache.sysds.runtime.controlprogram.context.ExecutionContext;
	import org.apache.sysds.runtime.instructions.Instruction;
	import org.apache.sysds.runtime.instructions.cp.BinaryCPInstruction;
	import org.apache.sysds.runtime.instructions.cp.BuiltinNaryCPInstruction;
	import org.apache.sysds.runtime.instructions.cp.CPInstruction;
	import org.apache.sysds.runtime.instructions.cp.CPOperand;
	import org.apache.sysds.runtime.instructions.cp.ComputationCPInstruction;
	import org.apache.sysds.runtime.instructions.cp.Data;
	import org.apache.sysds.runtime.instructions.cp.QuaternaryCPInstruction;
	import org.apache.sysds.runtime.instructions.cp.UnaryCPInstruction;
	import org.apache.sysds.runtime.instructions.cp.VariableCPInstruction;
	import org.apache.sysds.runtime.privacy.PrivacyConstraint.PrivacyLevel;
	import org.apache.wink.json4j.JSONException;
	import org.apache.wink.json4j.JSONObject;

	/**
	* Class with static methods merging privacy constraints of operands
	* in expressions to generate the privacy constraints of the output.
	*/
	public class PrivacyPropagator
	{
	public static CacheableData<?> parseAndSetPrivacyConstraint(CacheableData<?> cd, JSONObject mtd)
	throws JSONException
	{
	if ( mtd.containsKey(DataExpression.PRIVACY) ) {
	String privacyLevel = mtd.getString(DataExpression.PRIVACY);
	if ( privacyLevel != null )
	cd.setPrivacyConstraints(new PrivacyConstraint(PrivacyLevel.valueOf(privacyLevel)));
	}
	return cd;
	}

	public static PrivacyConstraint mergeBinary(PrivacyConstraint privacyConstraint1, PrivacyConstraint privacyConstraint2) {
	if (privacyConstraint1 != null && privacyConstraint2 != null){
	PrivacyLevel privacyLevel1 = privacyConstraint1.getPrivacyLevel();
	PrivacyLevel privacyLevel2 = privacyConstraint2.getPrivacyLevel();

	// One of the inputs are private, hence the output must be private.
	if (privacyLevel1 == PrivacyLevel.Private \|\| privacyLevel2 == PrivacyLevel.Private)
	return new PrivacyConstraint(PrivacyLevel.Private);
	// One of the inputs are private with aggregation allowed, but none of the inputs are completely private,
	// hence the output must be private with aggregation.
	else if (privacyLevel1 == PrivacyLevel.PrivateAggregation \|\| privacyLevel2 == PrivacyLevel.PrivateAggregation)
	return new PrivacyConstraint(PrivacyLevel.PrivateAggregation);
	// Both inputs have privacy level "None", hence the privacy constraint can be removed.
	else
	return null;
	}
	else if (privacyConstraint1 != null)
	return privacyConstraint1;
	else if (privacyConstraint2 != null)
	return privacyConstraint2;
	return null;
	}

	public static PrivacyConstraint mergeTernary(PrivacyConstraint[] privacyConstraints){
	return mergeBinary(mergeBinary(privacyConstraints[0], privacyConstraints[1]), privacyConstraints[2]);
	}

	public static PrivacyConstraint mergeQuaternary(PrivacyConstraint[] privacyConstraints){
	return mergeBinary(mergeTernary(privacyConstraints), privacyConstraints[3]);
	}

	public static PrivacyConstraint mergeNary(PrivacyConstraint[] privacyConstraints){
	PrivacyConstraint mergedPrivacyConstraint = privacyConstraints[0];
	for ( int i = 1; i < privacyConstraints.length; i++ ){
	mergedPrivacyConstraint = mergeBinary(mergedPrivacyConstraint, privacyConstraints[i]);
	}
	return mergedPrivacyConstraint;
	}

	public static Instruction preprocessInstruction(Instruction inst, ExecutionContext ec){
	switch ( inst.getType() ){
	case CONTROL_PROGRAM:
	return preprocessCPInstruction( (CPInstruction) inst, ec );
	case BREAKPOINT:
	case SPARK:
	case GPU:
	case FEDERATED:
	return inst;
	default:
	throwExceptionIfPrivacyActivated(inst, ec);
	return inst;
	}
	}

	public static Instruction preprocessCPInstruction(CPInstruction inst, ExecutionContext ec){
	switch ( inst.getCPInstructionType() )
	{
	case Variable:
	return preprocessVariableCPInstruction((VariableCPInstruction) inst, ec);
	case AggregateUnary:
	case Reorg:
	case Unary:
	return preprocessUnaryCPInstruction((UnaryCPInstruction) inst, ec);
	case AggregateBinary:
	case Append:
	case Binary:
	return preprocessBinaryCPInstruction((BinaryCPInstruction) inst, ec);
	case AggregateTernary:
	case Ternary:
	return preprocessTernaryCPInstruction((ComputationCPInstruction) inst, ec);
	case Quaternary:
	return preprocessQuaternary((QuaternaryCPInstruction) inst, ec);
	case BuiltinNary:
	case Builtin:
	return preprocessBuiltinNary((BuiltinNaryCPInstruction) inst, ec);
	case Ctable:
	case MultiReturnParameterizedBuiltin:
	case MultiReturnBuiltin:
	case ParameterizedBuiltin:
	default:
	return preprocessInstructionSimple(inst, ec);
	}
	}

	/**
	* Throw exception if privacy constraints are activated or return instruction if privacy is not activated
	* @param inst instruction
	* @param ec execution context
	* @return instruction
	*/
	public static Instruction preprocessInstructionSimple(Instruction inst, ExecutionContext ec){
	throwExceptionIfPrivacyActivated(inst, ec);
	return inst;
	}

	public static Instruction preprocessBuiltinNary(BuiltinNaryCPInstruction inst, ExecutionContext ec){
	if (inst.getInputs() == null) return inst;
	PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, inst.getInputs());
	PrivacyConstraint mergedPrivacyConstraint = mergeNary(privacyConstraints);
	inst.setPrivacyConstraint(mergedPrivacyConstraint);
	setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.getOutput());
	return inst;
	}

	public static Instruction preprocessQuaternary(QuaternaryCPInstruction inst, ExecutionContext ec){
	PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec,
	new CPOperand[] {inst.input1,inst.input2,inst.input3,inst.getInput4()});
	PrivacyConstraint mergedPrivacyConstraint = mergeQuaternary(privacyConstraints);
	inst.setPrivacyConstraint(mergedPrivacyConstraint);
	setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
	return inst;
	}

	public static Instruction preprocessTernaryCPInstruction(ComputationCPInstruction inst, ExecutionContext ec){
	PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, new CPOperand[]{inst.input1, inst.input2, inst.input3});
	PrivacyConstraint mergedPrivacyConstraint = mergeTernary(privacyConstraints);
	inst.setPrivacyConstraint(mergedPrivacyConstraint);
	setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
	return inst;
	}

	public static Instruction preprocessNaryInstruction(CPInstruction inst, ExecutionContext ec, CPOperand[] inputs, CPOperand output, Function<PrivacyConstraint[], PrivacyConstraint> mergeFunction){
	PrivacyConstraint[] privacyConstraints = getInputPrivacyConstraints(ec, inputs);
	PrivacyConstraint mergedPrivacyConstraint = mergeFunction.apply(privacyConstraints);
	inst.setPrivacyConstraint(mergedPrivacyConstraint);
	setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, output);
	return inst;

	}

	public static Instruction preprocessBinaryCPInstruction(BinaryCPInstruction inst, ExecutionContext ec){
	PrivacyConstraint privacyConstraint1 = getInputPrivacyConstraint(ec, inst.input1);
	PrivacyConstraint privacyConstraint2 = getInputPrivacyConstraint(ec, inst.input2);
	if ( privacyConstraint1 != null \|\| privacyConstraint2 != null)
	{
	PrivacyConstraint mergedPrivacyConstraint = mergeBinary(privacyConstraint1, privacyConstraint2);
	inst.setPrivacyConstraint(mergedPrivacyConstraint);
	setOutputPrivacyConstraint(ec, mergedPrivacyConstraint, inst.output);
	}
	return inst;
	}

	public static Instruction preprocessUnaryCPInstruction(UnaryCPInstruction inst, ExecutionContext ec){
	return propagateInputPrivacy(inst, ec, inst.input1, inst.output);
	}

	public static Instruction preprocessVariableCPInstruction(VariableCPInstruction inst, ExecutionContext ec){
	switch ( inst.getVariableOpcode() )
	{
	case CreateVariable:
	return propagateSecondInputPrivacy(inst, ec);
	case AssignVariable:
	//Assigns scalar, hence it does not have privacy activated
	return inst;
	case CopyVariable:
	case MoveVariable:
	return propagateFirstInputPrivacy(inst, ec);
	case RemoveVariable:
	return propagateAllInputPrivacy(inst, ec);
	case RemoveVariableAndFile:
	return propagateFirstInputPrivacy(inst, ec);
	case CastAsScalarVariable:
	return propagateCastAsScalarVariablePrivacy(inst, ec);
	case CastAsMatrixVariable:
	case CastAsFrameVariable:
	return propagateFirstInputPrivacy(inst, ec);
	case CastAsDoubleVariable:
	case CastAsIntegerVariable:
	case CastAsBooleanVariable:
	return propagateCastAsScalarVariablePrivacy(inst, ec);
	case Read:
	return inst;
	case Write:
	return propagateFirstInputPrivacy(inst, ec);
	case SetFileName:
	return propagateFirstInputPrivacy(inst, ec);
	default:
	throwExceptionIfPrivacyActivated(inst, ec);
	return inst;
	}
	}

	private static void throwExceptionIfPrivacyActivated(Instruction inst, ExecutionContext ec){
	if ( inst.getPrivacyConstraint() != null && inst.getPrivacyConstraint().getPrivacyLevel().equals(PrivacyLevel.Private) ) {
	throw new DMLPrivacyException("Instruction " + inst + " has privacy constraints activated, but the constraints are not propagated during preprocessing of instruction.");
	}
	}

	/**
	* Propagate privacy from first input and throw exception if privacy is activated.
	* @param inst Instruction
	* @param ec execution context
	* @return instruction with or without privacy constraints
	*/
	private static Instruction propagateCastAsScalarVariablePrivacy(VariableCPInstruction inst, ExecutionContext ec){
	inst = (VariableCPInstruction) propagateFirstInputPrivacy(inst, ec);
	return preprocessInstructionSimple(inst, ec);
	}

	/**
	* Propagate privacy constraints from all inputs if privacy constraints are set.
	* @param inst instruction
	* @param ec execution context
	* @return instruction with or without privacy constraints
	*/
	private static Instruction propagateAllInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
	//TODO: Propagate the most restricting constraints instead of just the latest activated constraint
	for ( CPOperand input : inst.getInputs() )
	inst = (VariableCPInstruction) propagateInputPrivacy(inst, ec, input, inst.getOutput());
	return inst;
	}

	/**
	* Propagate privacy constraint to instruction and output of instruction
	* if data of first input is CacheableData and
	* privacy constraint is activated.
	* @param inst VariableCPInstruction
	* @param ec execution context
	* @return instruction with or without privacy constraints
	*/
	private static Instruction propagateFirstInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
	return propagateInputPrivacy(inst, ec, inst.getInput1(), inst.getOutput());
	}

	/**
	* Propagate privacy constraint to instruction and output of instruction
	* if data of second input is CacheableData and
	* privacy constraint is activated.
	* @param inst VariableCPInstruction
	* @param ec execution context
	* @return instruction with or without privacy constraints
	*/
	private static Instruction propagateSecondInputPrivacy(VariableCPInstruction inst, ExecutionContext ec){
	return propagateInputPrivacy(inst, ec, inst.getInput2(), inst.getOutput());
	}

	/**
	* Propagate privacy constraint to instruction and output of instruction
	* if data of the specified variable is CacheableData
	* and privacy constraint is activated
	* @param inst instruction
	* @param ec execution context
	* @param inputOperand input from which the privacy constraint is found
	* @param outputOperand output which the privacy constraint is propagated to
	* @return instruction with or without privacy constraints
	*/
	private static Instruction propagateInputPrivacy(Instruction inst, ExecutionContext ec, CPOperand inputOperand, CPOperand outputOperand){
	PrivacyConstraint privacyConstraint = getInputPrivacyConstraint(ec, inputOperand);
	if ( privacyConstraint != null ) {
	inst.setPrivacyConstraint(privacyConstraint);
	if ( outputOperand != null)
	setOutputPrivacyConstraint(ec, privacyConstraint, outputOperand);
	}
	return inst;
	}

	private static PrivacyConstraint getInputPrivacyConstraint(ExecutionContext ec, CPOperand input){
	if ( input != null && input.getName() != null){
	Data dd = ec.getVariable(input.getName());
	if ( dd != null && dd instanceof CacheableData)
	return ((CacheableData<?>) dd).getPrivacyConstraint();
	}
	return null;
	}


	private static PrivacyConstraint[] getInputPrivacyConstraints(ExecutionContext ec, CPOperand[] inputs){
	PrivacyConstraint[] privacyConstraints = new PrivacyConstraint[inputs.length];
	for ( int i = 0; i < inputs.length; i++ ){
	privacyConstraints[i] = getInputPrivacyConstraint(ec, inputs[i]);
	}
	return privacyConstraints;

	}

	private static void setOutputPrivacyConstraint(ExecutionContext ec, PrivacyConstraint privacyConstraint, CPOperand output){
	Data dd = ec.getVariable(output.getName());
	if ( dd != null ){
	if ( dd instanceof CacheableData ){
	((CacheableData<?>) dd).setPrivacyConstraints(privacyConstraint);
	ec.setVariable(output.getName(), dd);
	}
	else throw new DMLPrivacyException("Privacy constraint of " + output + " cannot be set since it is not an instance of CacheableData");
	}
	}
	}