diff --git a/Sources/XXClient/Helpers/ConvertJsonNumberToString.swift b/Sources/XXClient/Helpers/ConvertJsonNumberToString.swift
deleted file mode 100644
index 8390ba1ced0f8a0aff92287b899a81fca0247c77..0000000000000000000000000000000000000000
--- a/Sources/XXClient/Helpers/ConvertJsonNumberToString.swift
+++ /dev/null
@@ -1,37 +0,0 @@
-import Foundation
-
-func convertJsonNumberToString(
-  in input: Data,
-  at key: String
-) -> Data {
-  guard var string = String(data: input, encoding: .utf8) else {
-    return input
-  }
-  string = string.replacingOccurrences(
-    of: #""\#(key)"( *):( *)([0-9]+)( *)(,*)"#,
-    with: #""\#(key)"$1:$2"$3"$4$5"#,
-    options: [.regularExpression]
-  )
-  guard let output = string.data(using: .utf8) else {
-    return input
-  }
-  return output
-}
-
-func convertJsonNumberToString(
-  in input: Data,
-  minNumberLength: Int
-) -> Data {
-  guard var string = String(data: input, encoding: .utf8) else {
-    return input
-  }
-  string = string.replacingOccurrences(
-    of: #":( *)([0-9]{\#(minNumberLength),})( *)(,*)"#,
-    with: #":$1"$2"$3$4"#,
-    options: [.regularExpression]
-  )
-  guard let output = string.data(using: .utf8) else {
-    return input
-  }
-  return output
-}
diff --git a/Sources/XXClient/Helpers/JSONHelpers.swift b/Sources/XXClient/Helpers/JSONHelpers.swift
new file mode 100644
index 0000000000000000000000000000000000000000..7527ac9ae217c188ff837501fd472b23ff478862
--- /dev/null
+++ b/Sources/XXClient/Helpers/JSONHelpers.swift
@@ -0,0 +1,85 @@
+import Foundation
+
+/// Replaces all numbers at provided key with string equivalents
+///
+/// Example input:
+/// {
+///   "key": 123,
+///   "object": {
+///     "hello": "world",
+///     "key": 321
+///   }
+/// }
+///
+/// Example output:
+/// {
+///   "key": "123",
+///   "object": {
+///     "hello": "world",
+///     "key": "321"
+///   }
+/// }
+///
+/// - Parameters:
+///   - input: JSON data
+///   - key: the key which values should be converted
+/// - Returns: JSON data
+func convertJsonNumberToString(
+  in input: Data,
+  at key: String
+) -> Data {
+  guard var string = String(data: input, encoding: .utf8) else {
+    return input
+  }
+  string = string.replacingOccurrences(
+    of: #""\#(key)"( *):( *)([0-9]+)( *)(,*)"#,
+    with: #""\#(key)"$1:$2"$3"$4$5"#,
+    options: [.regularExpression]
+  )
+  guard let output = string.data(using: .utf8) else {
+    return input
+  }
+  return output
+}
+
+/// Replaces all strings at provided key with number equivalents
+///
+/// Example input:
+/// {
+///   "key": "123",
+///   "object": {
+///     "hello": "world",
+///     "key": "321"
+///   }
+/// }
+///
+/// Example output:
+/// {
+///   "key": 123,
+///   "object": {
+///     "hello": "world",
+///     "key": 321
+///   }
+/// }
+///
+/// - Parameters:
+///   - input: JSON data
+///   - key: the key which values should be converted
+/// - Returns: JSON data
+func convertJsonStringToNumber(
+  in input: Data,
+  at key: String
+) -> Data {
+  guard var string = String(data: input, encoding: .utf8) else {
+    return input
+  }
+  string = string.replacingOccurrences(
+    of: #""\#(key)"( *):( *)"([0-9]+)"( *)(,*)"#,
+    with: #""\#(key)"$1:$2$3$4$5"#,
+    options: [.regularExpression]
+  )
+  guard let output = string.data(using: .utf8) else {
+    return input
+  }
+  return output
+}
diff --git a/Sources/XXClient/Models/DHKey.swift b/Sources/XXClient/Models/DHKey.swift
new file mode 100644
index 0000000000000000000000000000000000000000..5dc94983016cced7c2d4b2c0dc450c63f07acdcc
--- /dev/null
+++ b/Sources/XXClient/Models/DHKey.swift
@@ -0,0 +1,28 @@
+import Foundation
+
+public struct DHKey: Equatable {
+  public init(value: String, fingerprint: UInt64) {
+    self.value = value
+    self.fingerprint = fingerprint
+  }
+
+  public var value: String
+  public var fingerprint: UInt64
+}
+
+extension DHKey: Codable {
+  enum CodingKeys: String, CodingKey {
+    case value = "Value"
+    case fingerprint = "Fingerprint"
+  }
+
+  public static func decode(_ data: Data) throws -> Self {
+    let data = convertJsonNumberToString(in: data, at: "Value")
+    return try JSONDecoder().decode(Self.self, from: data)
+  }
+
+  public func encode() throws -> Data {
+    let data = try JSONEncoder().encode(self)
+    return convertJsonStringToNumber(in: data, at: "Value")
+  }
+}
diff --git a/Sources/XXClient/Models/GroupMember.swift b/Sources/XXClient/Models/GroupMember.swift
index 8ce7120a58880ab94f9f8a590ad6872565684bfd..cb5d9843bce2a661bdeb93560fbc77860b71d28c 100644
--- a/Sources/XXClient/Models/GroupMember.swift
+++ b/Sources/XXClient/Models/GroupMember.swift
@@ -1,27 +1,40 @@
 import Foundation
 
 public struct GroupMember: Equatable {
-  public init(id: Data) {
+  public init(id: Data, dhKey: DHKey) {
     self.id = id
+    self.dhKey = dhKey
   }
 
   public var id: Data
+  public var dhKey: DHKey
 }
 
-extension GroupMember: Decodable {
+extension GroupMember: Codable {
   enum CodingKeys: String, CodingKey {
     case id = "ID"
+    case dhKey = "DhKey"
   }
 
   public static func decode(_ data: Data) throws -> Self {
-    let data = convertJsonNumberToString(in: data, minNumberLength: 19)
+    let data = convertJsonNumberToString(in: data, at: "Value")
     return try JSONDecoder().decode(Self.self, from: data)
   }
+
+  public func encode() throws -> Data {
+    let data = try JSONEncoder().encode(self)
+    return convertJsonStringToNumber(in: data, at: "Value")
+  }
 }
 
 extension Array where Element == GroupMember {
   public static func decode(_ data: Data) throws -> Self {
-    let data = convertJsonNumberToString(in: data, minNumberLength: 19)
+    let data = convertJsonNumberToString(in: data, at: "Value")
     return try JSONDecoder().decode(Self.self, from: data)
   }
+
+  public func encode() throws -> Data {
+    let data = try JSONEncoder().encode(self)
+    return convertJsonStringToNumber(in: data, at: "Value")
+  }
 }
diff --git a/Tests/XXClientTests/Helpers/ConvertJsonNumberToStringTests.swift b/Tests/XXClientTests/Helpers/JSONHelpersTests.swift
similarity index 52%
rename from Tests/XXClientTests/Helpers/ConvertJsonNumberToStringTests.swift
rename to Tests/XXClientTests/Helpers/JSONHelpersTests.swift
index 4fc1ecd7f1b729f65f934d11adcac502c0127cf4..2ebe853034c56ea04fcbb52791fe6dbd56c079b2 100644
--- a/Tests/XXClientTests/Helpers/ConvertJsonNumberToStringTests.swift
+++ b/Tests/XXClientTests/Helpers/JSONHelpersTests.swift
@@ -2,33 +2,33 @@ import CustomDump
 import XCTest
 @testable import XXClient
 
-final class ConvertJsonNumberToStringTests: XCTestCase {
-  func testConverting() {
-    assert(
+final class JSONHelpersTests: XCTestCase {
+  func testConvertingNumberToStringByKey() {
+    assertConvertingJsonNumberToString(
       input: #"{"number":1234567890,"text":"hello"}"#,
       key: "number",
       expected: #"{"number":"1234567890","text":"hello"}"#
     )
 
-    assert(
+    assertConvertingJsonNumberToString(
       input: #"{"text":"hello","number":1234567890}"#,
       key: "number",
       expected: #"{"text":"hello","number":"1234567890"}"#
     )
 
-    assert(
+    assertConvertingJsonNumberToString(
       input: #"{  "number"  :  1234567890  ,  "text"  :  "hello"  }"#,
       key: "number",
       expected: #"{  "number"  :  "1234567890"  ,  "text"  :  "hello"  }"#
     )
 
-    assert(
+    assertConvertingJsonNumberToString(
       input: #"{  "text"  :  "hello"  ,  "number"  :  1234567890  }"#,
       key: "number",
       expected: #"{  "text"  :  "hello"  ,  "number"  :  "1234567890"  }"#
     )
 
-    assert(
+    assertConvertingJsonNumberToString(
       input: """
       {
         "number": 1234567890,
@@ -44,7 +44,7 @@ final class ConvertJsonNumberToStringTests: XCTestCase {
       """
     )
 
-    assert(
+    assertConvertingJsonNumberToString(
       input: """
       {
         "text": "hello",
@@ -59,32 +59,68 @@ final class ConvertJsonNumberToStringTests: XCTestCase {
       }
       """
     )
+  }
+
+  func testConvertingStringToNumber() {
+    assertConvertingJsonStringToNumber(
+      input: #"{"number":"1234567890","text":"hello"}"#,
+      key: "number",
+      expected: #"{"number":1234567890,"text":"hello"}"#
+    )
+
+    assertConvertingJsonStringToNumber(
+      input: #"{"text":"hello","number":"1234567890"}"#,
+      key: "number",
+      expected: #"{"text":"hello","number":1234567890}"#
+    )
+
+    assertConvertingJsonStringToNumber(
+      input: #"{  "number"  :  "1234567890"  ,  "text"  :  "hello"  }"#,
+      key: "number",
+      expected: #"{  "number"  :  1234567890  ,  "text"  :  "hello"  }"#
+    )
+
+    assertConvertingJsonStringToNumber(
+      input: #"{  "text"  :  "hello"  ,  "number"  :  "1234567890"  }"#,
+      key: "number",
+      expected: #"{  "text"  :  "hello"  ,  "number"  :  1234567890  }"#
+    )
+
+    assertConvertingJsonStringToNumber(
+      input: """
+      {
+        "number": "1234567890",
+        "text": "hello"
+      }
+      """,
+      key: "number",
+      expected: """
+      {
+        "number": 1234567890,
+        "text": "hello"
+      }
+      """
+    )
 
-    assert(
+    assertConvertingJsonStringToNumber(
       input: """
       {
         "text": "hello",
-        "number1": 123456789,
-        "number2": 1234567890,
-        "number3": 123456789,
-        "number4": 1234567890
+        "number": "1234567890"
       }
       """,
-      minNumberLength: 10,
+      key: "number",
       expected: """
       {
         "text": "hello",
-        "number1": 123456789,
-        "number2": "1234567890",
-        "number3": 123456789,
-        "number4": "1234567890"
+        "number": 1234567890
       }
       """
     )
   }
 }
 
-private func assert(
+private func assertConvertingJsonNumberToString(
   input: String,
   key: String,
   expected: String,
@@ -105,18 +141,18 @@ private func assert(
   )
 }
 
-private func assert(
+private func assertConvertingJsonStringToNumber(
   input: String,
-  minNumberLength: Int,
+  key: String,
   expected: String,
   file: StaticString = #file,
   line: UInt = #line
 ) {
   XCTAssertNoDifference(
     String(
-      data: convertJsonNumberToString(
+      data: convertJsonStringToNumber(
         in: input.data(using: .utf8)!,
-        minNumberLength: minNumberLength
+        at: key
       ),
       encoding: .utf8
     )!,
diff --git a/Tests/XXClientTests/Models/DHKeyTests.swift b/Tests/XXClientTests/Models/DHKeyTests.swift
new file mode 100644
index 0000000000000000000000000000000000000000..eea82bf385ff766676d881c5ae930c6a965f5668
--- /dev/null
+++ b/Tests/XXClientTests/Models/DHKeyTests.swift
@@ -0,0 +1,31 @@
+import CustomDump
+import XCTest
+@testable import XXClient
+
+final class DHKeyTests: XCTestCase {
+  func testCoding() throws {
+    let value = "1759426033802606996617132861414734059978289057332806031357800676138355264622676606691435603603751978195460163638145821347601916259127578968570412642641025630452893097179266022832268525346700655861033031712000288680395716922501450233258587788020541937373196899001184700899008948530359980753630443486308876999029238453979779103124291315202352475056237021681172884599194016245219278368648568458514708567045834427853469072638665888791358582182353417065794210125797368093469194927663862565508608719835557592421245749381164023134450699040591219966988201315627676532245052123725278573237006510683695959381015415110970848376498637637944431576313526294020390694483472829278364602405292767170719547347485307956614210210673321959886410245334772057212077704024337636501108566655549055129066343309591274727538343075929837698653965640646190405582788894021694347212874155979958144038307500444865955516612526623220973497735316081265793063949"
+    let fingerprint: UInt64 = 15989433043166758754
+    let jsonString = """
+    {
+      "Value": \(value),
+      "Fingerprint": \(fingerprint)
+    }
+    """
+    let jsonData = jsonString.data(using: .utf8)!
+    let model = try DHKey.decode(jsonData)
+
+    XCTAssertNoDifference(model, DHKey(
+      value: value,
+      fingerprint: fingerprint
+    ))
+
+    let encodedModel = try model.encode()
+    let encodedModelString = String(data: encodedModel, encoding: .utf8)
+
+    XCTAssertNoDifference(
+      encodedModelString,
+      #"{"Value":\#(value),"Fingerprint":\#(fingerprint)}"#
+    )
+  }
+}
diff --git a/Tests/XXClientTests/Models/GroupMemberTests.swift b/Tests/XXClientTests/Models/GroupMemberTests.swift
index 36e178c08f37b0bec719f4c3b7747043a9920491..eed1a4739d05b5832a40867c4842ccb18a280903 100644
--- a/Tests/XXClientTests/Models/GroupMemberTests.swift
+++ b/Tests/XXClientTests/Models/GroupMemberTests.swift
@@ -4,13 +4,15 @@ import XCTest
 
 final class GroupMemberTests: XCTestCase {
   func testCoding() throws {
-    let idB64 = "U4x/lrFkvxuXu59LtHLon1sUhPJSCcnZND6SugndnVID"
+    let idB64 = "SGVsbG8sIFdvcmxkISBHcm91cCBNZW1iZXIgVGVzdCBJRA=="
+    let dhKeyValue = "1759426033802606996617132861414734059978289057332806031357800676138355264622676606691435603603751978195460163638145821347601916259127578968570412642641025630452893097179266022832268525346700655861033031712000288680395716922501450233258587788020541937373196899001184700899008948530359980753630443486308876999029238453979779103124291315202352475056237021681172884599194016245219278368648568458514708567045834427853469072638665888791358582182353417065794210125797368093469194927663862565508608719835557592421245749381164023134450699040591219966988201315627676532245052123725278573237006510683695959381015415110970848376498637637944431576313526294020390694483472829278364602405292767170719547347485307956614210210673321959886410245334772057212077704024337636501108566655549055129066343309591274727538343075929837698653965640646190405582788894021694347212874155979958144038307500444865955516612526623220973497735316081265793063949"
+    let dhKeyFingerprint: UInt64 = 15989433043166758754
     let jsonString = """
     {
       "ID": "\(idB64)",
       "DhKey": {
-        "Value": 1759426033802606996617132861414734059978289057332806031357800676138355264622676606691435603603751978195460163638145821347601916259127578968570412642641025630452893097179266022832268525346700655861033031712000288680395716922501450233258587788020541937373196899001184700899008948530359980753630443486308876999029238453979779103124291315202352475056237021681172884599194016245219278368648568458514708567045834427853469072638665888791358582182353417065794210125797368093469194927663862565508608719835557592421245749381164023134450699040591219966988201315627676532245052123725278573237006510683695959381015415110970848376498637637944431576313526294020390694483472829278364602405292767170719547347485307956614210210673321959886410245334772057212077704024337636501108566655549055129066343309591274727538343075929837698653965640646190405582788894021694347212874155979958144038307500444865955516612526623220973497735316081265793063949,
-        "Fingerprint": 15989433043166758754
+        "Value": \(dhKeyValue),
+        "Fingerprint": \(dhKeyFingerprint)
       }
     }
     """
@@ -18,13 +20,34 @@ final class GroupMemberTests: XCTestCase {
     let model = try GroupMember.decode(jsonData)
 
     XCTAssertNoDifference(model, GroupMember(
-      id: Data(base64Encoded: idB64)!
+      id: Data(base64Encoded: idB64)!,
+      dhKey: DHKey(
+        value: dhKeyValue,
+        fingerprint: dhKeyFingerprint
+      )
     ))
 
+    let encodedModel = try model.encode()
+    let encodedModelString = String(data: encodedModel, encoding: .utf8)!
+    XCTAssertNoDifference(
+      encodedModelString,
+      """
+      {"ID":"\(idB64)","DhKey":{"Value":\(dhKeyValue),"Fingerprint":\(dhKeyFingerprint)}}
+      """
+    )
+
     let jsonArrayString = "[\(jsonString)]"
     let jsonArrayData = jsonArrayString.data(using: .utf8)!
     let decodedModels = try [GroupMember].decode(jsonArrayData)
 
     XCTAssertNoDifference(decodedModels, [model])
+
+    let encodedModels = try decodedModels.encode()
+    let encodedModelsString = String(data: encodedModels, encoding: .utf8)!
+
+    XCTAssertNoDifference(
+      encodedModelsString,
+      "[\(encodedModelString)]"
+    )
   }
 }