diff --git a/keyserver/src/utils/validation-utils.js b/keyserver/src/utils/validation-utils.js
index df33ac7a4..6e618289b 100644
--- a/keyserver/src/utils/validation-utils.js
+++ b/keyserver/src/utils/validation-utils.js
@@ -1,260 +1,329 @@
 // @flow
 
 import _mapKeys from 'lodash/fp/mapKeys.js';
 import _mapValues from 'lodash/fp/mapValues.js';
 import type { TType, TInterface } from 'tcomb';
 
 import type { PolicyType } from 'lib/facts/policies.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
+import { isWebPlatform } from 'lib/types/device-types.js';
 import { ServerError } from 'lib/utils/errors.js';
 import {
   tCookie,
   tPassword,
   tPlatform,
   tPlatformDetails,
   assertWithValidator,
+  tID,
 } from 'lib/utils/validation-utils.js';
 
 import { fetchNotAcknowledgedPolicies } from '../fetchers/policy-acknowledgment-fetchers.js';
 import { verifyClientSupported } from '../session/version.js';
 import type { Viewer } from '../session/viewer.js';
 
 async function validateInput<T>(
   viewer: Viewer,
   inputValidator: ?TType<T>,
   input: T,
 ) {
   if (!viewer.isSocket) {
     await checkClientSupported(viewer, inputValidator, input);
   }
   checkInputValidator(inputValidator, input);
 }
 
+const convertToNewIDSchema = false;
+const keyserverPrefixID = '256';
+
+function validateOutput<T>(
+  viewer: Viewer,
+  outputValidator: TType<T>,
+  data: T,
+): T {
+  if (!outputValidator.is(data)) {
+    console.trace(
+      'Output validation failed, validator is:',
+      outputValidator.displayName,
+    );
+    return data;
+  }
+
+  if (
+    hasMinCodeVersion(viewer.platformDetails, 1000) &&
+    !isWebPlatform(viewer.platformDetails?.platform) &&
+    convertToNewIDSchema
+  ) {
+    return convertServerIDsToClientIDs(
+      keyserverPrefixID,
+      outputValidator,
+      data,
+    );
+  }
+
+  return data;
+}
+
+function convertServerIDsToClientIDs<T>(
+  serverPrefixID: string,
+  outputValidator: TType<T>,
+  data: T,
+): T {
+  const conversionFunction = id => {
+    if (id.indexOf('|') !== -1) {
+      console.warn(`Server id '${id}' already has a prefix`);
+      return id;
+    }
+    return `${serverPrefixID}|${id}`;
+  };
+
+  return convertObject(outputValidator, data, [tID], conversionFunction);
+}
+
+function convertClientIDsToServerIDs<T>(
+  serverPrefixID: string,
+  outputValidator: TType<T>,
+  data: T,
+): T {
+  const prefix = serverPrefixID + '|';
+  const conversionFunction = id => {
+    if (id.startsWith(prefix)) {
+      return id.substr(prefix.length);
+    }
+
+    throw new ServerError('invalid_client_id_prefix');
+  };
+
+  return convertObject(outputValidator, data, [tID], conversionFunction);
+}
+
 function checkInputValidator<T>(inputValidator: ?TType<T>, input: T) {
   if (!inputValidator || inputValidator.is(input)) {
     return;
   }
   const error = new ServerError('invalid_parameters');
   error.sanitizedInput = input ? sanitizeInput(inputValidator, input) : null;
   throw error;
 }
 
 async function checkClientSupported<T>(
   viewer: Viewer,
   inputValidator: ?TType<T>,
   input: T,
 ) {
   let platformDetails;
   if (inputValidator) {
     platformDetails = findFirstInputMatchingValidator(
       inputValidator,
       tPlatformDetails,
       input,
     );
   }
   if (!platformDetails && inputValidator) {
     const platform = findFirstInputMatchingValidator(
       inputValidator,
       tPlatform,
       input,
     );
     if (platform) {
       platformDetails = { platform };
     }
   }
   if (!platformDetails) {
     ({ platformDetails } = viewer);
   }
   await verifyClientSupported(viewer, platformDetails);
 }
 
 const redactedString = '********';
 const redactedTypes = [tPassword, tCookie];
 function sanitizeInput<T>(inputValidator: TType<T>, input: T): T {
   return convertObject(
     inputValidator,
     input,
     redactedTypes,
     () => redactedString,
   );
 }
 
 function findFirstInputMatchingValidator(
   wholeInputValidator: *,
   inputValidatorToMatch: *,
   input: *,
 ): any {
   if (!wholeInputValidator || input === null || input === undefined) {
     return null;
   }
   if (
     wholeInputValidator === inputValidatorToMatch &&
     wholeInputValidator.is(input)
   ) {
     return input;
   }
   if (wholeInputValidator.meta.kind === 'maybe') {
     return findFirstInputMatchingValidator(
       wholeInputValidator.meta.type,
       inputValidatorToMatch,
       input,
     );
   }
   if (
     wholeInputValidator.meta.kind === 'interface' &&
     typeof input === 'object'
   ) {
     for (const key in input) {
       const value = input[key];
       const validator = wholeInputValidator.meta.props[key];
       const innerResult = findFirstInputMatchingValidator(
         validator,
         inputValidatorToMatch,
         value,
       );
       if (innerResult) {
         return innerResult;
       }
     }
   }
   if (wholeInputValidator.meta.kind === 'union') {
     for (const validator of wholeInputValidator.meta.types) {
       if (validator.is(input)) {
         return findFirstInputMatchingValidator(
           validator,
           inputValidatorToMatch,
           input,
         );
       }
     }
   }
   if (wholeInputValidator.meta.kind === 'list' && Array.isArray(input)) {
     const validator = wholeInputValidator.meta.type;
     for (const value of input) {
       const innerResult = findFirstInputMatchingValidator(
         validator,
         inputValidatorToMatch,
         value,
       );
       if (innerResult) {
         return innerResult;
       }
     }
   }
   return null;
 }
 
 function convertObject<T, I>(
   validator: TType<I>,
   input: I,
   typesToConvert: $ReadOnlyArray<TType<T>>,
   conversionFunction: T => T,
 ): I {
   if (input === null || input === undefined) {
     return input;
   }
 
   // While they should be the same runtime object,
   // `TValidator` is `TType<T>` and `validator` is `TType<I>`.
   // Having them have different types allows us to use `assertWithValidator`
   // to change `input` flow type
   const TValidator = typesToConvert[typesToConvert.indexOf(validator)];
   if (TValidator && TValidator.is(input)) {
     const TInput = assertWithValidator(input, TValidator);
     const converted = conversionFunction(TInput);
     return assertWithValidator(converted, validator);
   }
 
   if (validator.meta.kind === 'maybe') {
     return convertObject(
       validator.meta.type,
       input,
       typesToConvert,
       conversionFunction,
     );
   }
   if (validator.meta.kind === 'interface' && typeof input === 'object') {
     const recastValidator: TInterface<typeof input> = (validator: any);
     const result = {};
     for (const key in input) {
       const innerValidator = recastValidator.meta.props[key];
       result[key] = convertObject(
         innerValidator,
         input[key],
         typesToConvert,
         conversionFunction,
       );
     }
     return assertWithValidator(result, recastValidator);
   }
   if (validator.meta.kind === 'union') {
     for (const innerValidator of validator.meta.types) {
       if (innerValidator.is(input)) {
         return convertObject(
           innerValidator,
           input,
           typesToConvert,
           conversionFunction,
         );
       }
     }
     return input;
   }
   if (validator.meta.kind === 'list' && Array.isArray(input)) {
     const innerValidator = validator.meta.type;
     return (input.map(value =>
       convertObject(innerValidator, value, typesToConvert, conversionFunction),
     ): any);
   }
   if (validator.meta.kind === 'dict' && typeof input === 'object') {
     const domainValidator = validator.meta.domain;
     const codomainValidator = validator.meta.codomain;
     if (typesToConvert.includes(domainValidator)) {
       input = _mapKeys(key => conversionFunction(key))(input);
     }
     return _mapValues(value =>
       convertObject(
         codomainValidator,
         value,
         typesToConvert,
         conversionFunction,
       ),
     )(input);
   }
 
   return input;
 }
 
 async function policiesValidator(
   viewer: Viewer,
   policies: $ReadOnlyArray<PolicyType>,
 ) {
   if (!policies.length) {
     return;
   }
   if (!hasMinCodeVersion(viewer.platformDetails, 181)) {
     return;
   }
 
   const notAcknowledgedPolicies = await fetchNotAcknowledgedPolicies(
     viewer.id,
     policies,
   );
 
   if (notAcknowledgedPolicies.length) {
     throw new ServerError('policies_not_accepted', {
       notAcknowledgedPolicies,
     });
   }
 }
 
 export {
   validateInput,
+  validateOutput,
   checkInputValidator,
   redactedString,
   sanitizeInput,
   findFirstInputMatchingValidator,
   checkClientSupported,
+  convertServerIDsToClientIDs,
+  convertClientIDsToServerIDs,
   convertObject,
   policiesValidator,
 };
diff --git a/keyserver/src/utils/validation-utils.test.js b/keyserver/src/utils/validation-utils.test.js
index 244e5c6e2..5967f20f0 100644
--- a/keyserver/src/utils/validation-utils.test.js
+++ b/keyserver/src/utils/validation-utils.test.js
@@ -1,74 +1,109 @@
 // @flow
 
 import t from 'tcomb';
 
-import { tPassword, tShape } from 'lib/utils/validation-utils.js';
+import { tPassword, tShape, tID } from 'lib/utils/validation-utils.js';
 
-import { sanitizeInput, redactedString } from './validation-utils.js';
+import {
+  convertServerIDsToClientIDs,
+  sanitizeInput,
+  redactedString,
+  convertClientIDsToServerIDs,
+} from './validation-utils.js';
 
 describe('sanitization', () => {
   it('should redact a string', () => {
     expect(sanitizeInput(tPassword, 'password')).toStrictEqual(redactedString);
   });
 
   it('should redact a string inside an object', () => {
     const validator = tShape({ password: tPassword });
     const object = { password: 'password' };
     const redacted = { password: redactedString };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact an optional string', () => {
     const validator = tShape({ password: t.maybe(tPassword) });
     const object = { password: 'password' };
     const redacted = { password: redactedString };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact a string in optional object', () => {
     const validator = tShape({ obj: t.maybe(tShape({ password: tPassword })) });
     const object = { obj: { password: 'password' } };
     const redacted = { obj: { password: redactedString } };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact a string array', () => {
     const validator = tShape({ passwords: t.list(tPassword) });
     const object = { passwords: ['password', 'password'] };
     const redacted = { passwords: [redactedString, redactedString] };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact a string inside a dict', () => {
     const validator = tShape({ passwords: t.dict(t.String, tPassword) });
     const object = { passwords: { a: 'password', b: 'password' } };
     const redacted = { passwords: { a: redactedString, b: redactedString } };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact password dict key', () => {
     const validator = tShape({ passwords: t.dict(tPassword, t.Bool) });
     const object = { passwords: { password1: true, password2: false } };
     const redacted = { passwords: {} };
     redacted.passwords[redactedString] = false;
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact a string inside a union', () => {
     const validator = tShape({
       password: t.union([tPassword, t.String, t.Bool]),
     });
     const object = { password: 'password' };
     const redacted = { password: redactedString };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 
   it('should redact a string inside an object array', () => {
     const validator = tShape({
       passwords: t.list(tShape({ password: tPassword })),
     });
     const object = { passwords: [{ password: 'password' }] };
     const redacted = { passwords: [{ password: redactedString }] };
     expect(sanitizeInput(validator, object)).toStrictEqual(redacted);
   });
 });
+
+describe('id conversion', () => {
+  it('should convert string id', () => {
+    const validator = tShape({ id: tID });
+    const serverData = { id: '1' };
+    const clientData = { id: '0|1' };
+
+    expect(
+      convertServerIDsToClientIDs('0', validator, serverData),
+    ).toStrictEqual(clientData);
+    expect(
+      convertClientIDsToServerIDs('0', validator, clientData),
+    ).toStrictEqual(serverData);
+  });
+
+  it('should convert a complex type', () => {
+    const validator = tShape({ ids: t.dict(tID, t.list(tID)) });
+    const serverData = { ids: { '1': ['11', '12'], '2': [], '3': ['13'] } };
+    const clientData = {
+      ids: { '0|1': ['0|11', '0|12'], '0|2': [], '0|3': ['0|13'] },
+    };
+
+    expect(
+      convertServerIDsToClientIDs('0', validator, serverData),
+    ).toStrictEqual(clientData);
+    expect(
+      convertClientIDsToServerIDs('0', validator, clientData),
+    ).toStrictEqual(serverData);
+  });
+});