diff --git a/Package.swift b/Package.swift
index 95cc3be..09e86e3 100644
--- a/Package.swift
+++ b/Package.swift
@@ -12,7 +12,8 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/attaswift/BigInt", .exact("5.3.0")),
-        .package(url: "https://github.com/bitmark-inc/tweetnacl-swiftwrap", .upToNextMajor(from: "1.0.0"))
+        .package(url: "https://github.com/bitmark-inc/tweetnacl-swiftwrap", .upToNextMajor(from: "1.0.0")),
+        .package(url: "https://github.com/jedisct1/swift-sodium", .exact("0.9.1"))
     ],
     targets: [
         .target(
@@ -20,6 +21,7 @@ let package = Package(
             dependencies: [
                 .product(name: "BigInt", package: "BigInt"),
                 .product(name: "TweetNacl", package: "tweetnacl-swiftwrap"),
+                .product(name: "Sodium", package: "swift-sodium"),
             ]),
         .testTarget(
             name: "TonSwiftTests",
diff --git a/Source/TonSwift/CommentEncryption/CommentDecryptor.swift b/Source/TonSwift/CommentEncryption/CommentDecryptor.swift
new file mode 100644
index 0000000..8abebae
--- /dev/null
+++ b/Source/TonSwift/CommentEncryption/CommentDecryptor.swift
@@ -0,0 +1,77 @@
+import Foundation
+
+public struct CommentDecryptor {
+  enum Error: Swift.Error {
+    case incorrectCipherData
+    case incorrectCipherDataLength
+    case failedGetSharedSecret(error: Swift.Error)
+    case incorrectEncryptedDataSize
+    case incorrectHash
+    case incorrectPrefixSize
+  }
+  
+  private let privateKey: PrivateKey
+  private let publicKey: PublicKey
+  private let cipherText: String
+  private let senderAddress: Address
+  
+  public init(privateKey: PrivateKey,
+              publicKey: PublicKey,
+              cipherText: String,
+              senderAddress: Address) {
+    self.privateKey = privateKey
+    self.publicKey = publicKey
+    self.cipherText = cipherText
+    self.senderAddress = senderAddress
+  }
+  
+  public func decrypt() throws -> String? {
+    guard let cipherTextData = Data(hex: cipherText) else {
+      throw Error.incorrectCipherData
+    }
+    
+    let cipherTextBytes = [UInt8](cipherTextData)
+    guard cipherTextBytes.count >= publicKey.data.count else {
+      throw Error.incorrectCipherDataLength
+    }
+    let cipherTextPublicKeyBytes = Array(cipherTextBytes[0..<publicKey.data.count])
+    let encryptedData = Array(cipherTextBytes[publicKey.data.count..<cipherTextBytes.count])
+    guard encryptedData.count >= 16, encryptedData.count % 16 == 0 else {
+      throw Error.incorrectEncryptedDataSize
+    }
+    
+    let senderPublicKey = PublicKey(data: Data([UInt8](publicKey.data).enumerated().map { $0.element ^ cipherTextPublicKeyBytes[$0.offset] }))
+    let sharedSecret: Data
+    do {
+      sharedSecret = try Ed25519.getSharedSecret(privateKey: privateKey, publicKey: senderPublicKey)
+    } catch {
+      throw Error.failedGetSharedSecret(error: error)
+    }
+  
+    let msgKey = Data(Array(encryptedData[0..<16]))
+    let data = Data(Array(encryptedData[16..<encryptedData.count]))
+    
+    let cbcStateSecret = HMAC_SHA512.hmacSha512(message: msgKey, key: sharedSecret)
+    
+    let aesKey = cbcStateSecret[0..<32]
+    let iv = cbcStateSecret[32..<48]
+    let decryptedData = try AES_CBC(key: aesKey, iv: iv).decrypt(cipherData: data)
+  
+    let salt = senderAddress.toFriendly(testOnly: false, bounceable: true).toString().data(using: .utf8) ?? Data()
+    
+    let decryptedDataHash = HMAC_SHA512.hmacSha512(message: decryptedData, key: salt)
+    
+    let encryptionMsgKey = decryptedDataHash[0..<16]
+    guard encryptionMsgKey == msgKey else {
+      throw Error.incorrectHash
+    }
+    
+    let prefixLength = Int(decryptedData[0])
+    guard prefixLength <= decryptedData.count && prefixLength >= 16 else {
+      throw Error.incorrectPrefixSize
+    }
+    
+    let decryptedMessage = decryptedData[prefixLength..<decryptedData.count]
+    return String(data: decryptedMessage, encoding: .utf8)
+  }
+}
diff --git a/Source/TonSwift/CommentEncryption/CommentEncryptor.swift b/Source/TonSwift/CommentEncryption/CommentEncryptor.swift
new file mode 100644
index 0000000..5bafd63
--- /dev/null
+++ b/Source/TonSwift/CommentEncryption/CommentEncryptor.swift
@@ -0,0 +1,70 @@
+import Foundation
+
+public struct CommentEncryptor {
+  enum Error: Swift.Error {
+    case commentIsEmpty
+    case failedGetSharedSecret(error: Swift.Error)
+    case incorrectDataSize
+  }
+  
+  private let comment: String
+  private let senderPublicKey: PublicKey
+  private let senderPrivateKey: PrivateKey
+  private let peerPublicKey: PublicKey
+  private let senderAddress: Address
+  
+  public init(comment: String,
+              senderPublicKey: PublicKey,
+              senderPrivateKey: PrivateKey,
+              peerPublicKey: PublicKey,
+              senderAddress: Address) {
+    self.comment = comment
+    self.senderPublicKey = senderPublicKey
+    self.senderPrivateKey = senderPrivateKey
+    self.peerPublicKey = peerPublicKey
+    self.senderAddress = senderAddress
+  }
+  
+  public func encrypt() throws -> Data {
+    guard !comment.isEmpty else {
+      throw Error.commentIsEmpty
+    }
+    
+    let commentData = comment.data(using: .utf8) ?? Data()
+    let salt = senderAddress.toFriendly(testOnly: false, bounceable: true).toString().data(using: .utf8) ?? Data()
+    
+    let sharedSecret: Data
+    do {
+      sharedSecret = try Ed25519.getSharedSecret(privateKey: senderPrivateKey, publicKey: peerPublicKey)
+    } catch {
+      throw Error.failedGetSharedSecret(error: error)
+    }
+    
+    let prefix = try getRandomPrefix(dataLength: commentData.count, minPadding: 16)
+    let data = prefix + commentData
+    
+    guard data.count % 16 == 0 else { throw Error.incorrectDataSize }
+    
+    let dataHash = HMAC_SHA512.hmacSha512(message: data, key: salt)
+    let msgKey = dataHash[0..<16]
+    let cbcStateSecret = HMAC_SHA512.hmacSha512(message: msgKey, key: sharedSecret)
+    
+    let aesKey = cbcStateSecret[0..<32]
+    let iv = cbcStateSecret[32..<48]
+    let encrypted = try AES_CBC(key: aesKey, iv: iv).encrypt(data: data)
+    
+    let encryptedData = msgKey + encrypted
+    
+    let cipherTextPrefix = peerPublicKey.data.enumerated().map { $0.element ^ senderPublicKey.data[$0.offset] }
+    let cipherTextData = Data(cipherTextPrefix + encryptedData)
+    
+    return cipherTextData
+  }
+  
+  private func getRandomPrefix(dataLength: Int, minPadding: Int) throws -> Data {
+    let prefixLength = ((minPadding + 15 + dataLength) & -16) - dataLength
+    var prefix = try RandomBytes.generate(length: prefixLength)
+    prefix[0] = withUnsafeBytes(of: prefixLength.littleEndian, Array.init)[0]
+    return prefix
+  }
+}
diff --git a/Source/TonSwift/CommentEncryption/EncryptedCommentCellBuilder.swift b/Source/TonSwift/CommentEncryption/EncryptedCommentCellBuilder.swift
new file mode 100644
index 0000000..a600d35
--- /dev/null
+++ b/Source/TonSwift/CommentEncryption/EncryptedCommentCellBuilder.swift
@@ -0,0 +1,11 @@
+import Foundation
+
+public struct EncryptedCommentCellBuilder {
+  public static func buildCell(encryptedData: Data) throws -> Cell {
+    let opCodeData = Data(withUnsafeBytes(of: OpCodes.ENCRYPTED_COMMENT.bigEndian, Array.init))
+    let payloadData = opCodeData + encryptedData
+    
+    let builder = Builder()
+    return try builder.writeSnakeData(payloadData).endCell()
+  }
+}
diff --git a/Source/TonSwift/Crypto/25519/Ed25519.swift b/Source/TonSwift/Crypto/25519/Ed25519.swift
new file mode 100644
index 0000000..31a27dc
--- /dev/null
+++ b/Source/TonSwift/Crypto/25519/Ed25519.swift
@@ -0,0 +1,17 @@
+import Foundation
+
+public enum Ed25519 {
+  public enum Error: Swift.Error {
+    case sharedSecretError(Swift.Error)
+  }
+  
+  public static func getSharedSecret(privateKey: PrivateKey, publicKey: PublicKey) throws -> Data {
+    do {
+      let xPrivateKey = try privateKey.toX25519
+      let xPublicKey = try publicKey.toX25519
+      return try X25519.getSharedSecret(privateKey: xPrivateKey, publicKey: xPublicKey)
+    } catch {
+      throw Error.sharedSecretError(error)
+    }
+  }
+}
diff --git a/Source/TonSwift/Crypto/25519/X25519.swift b/Source/TonSwift/Crypto/25519/X25519.swift
new file mode 100644
index 0000000..6f861e9
--- /dev/null
+++ b/Source/TonSwift/Crypto/25519/X25519.swift
@@ -0,0 +1,84 @@
+import Foundation
+import Clibsodium
+
+public enum X25519 {
+  enum Error: Swift.Error {
+    case sharedSecretError(code: Int)
+  }
+  
+  public struct PrivateKey: Key, Equatable, Codable {
+    public let data: Data
+    
+    public init(data: Data) {
+      self.data = data
+    }
+  }
+  
+  public struct PublicKey: Key, Equatable, Codable {
+    public let data: Data
+    
+    public init(data: Data) {
+      self.data = data
+    }
+  }
+  
+  static func getSharedSecret(privateKey: X25519.PrivateKey, publicKey: X25519.PublicKey) throws -> Data {
+    var outputBuffer = Array<UInt8>(repeating: 0, count: .sharedSecretLength)
+    try privateKey.data.withUnsafeBytes { bufferPointer in
+      guard let privateKeyPointer = bufferPointer.baseAddress else { return }
+      try publicKey.data.withUnsafeBytes { bufferPointer in
+        guard let publicKeyPointer = bufferPointer.baseAddress else { return }
+        let statusCode = crypto_scalarmult(&outputBuffer, privateKeyPointer, publicKeyPointer)
+        guard statusCode == 0 else {
+          throw Error.sharedSecretError(code: Int(statusCode))
+        }
+      }
+    }
+    return Data(outputBuffer)
+  }
+}
+
+public extension X25519 {
+  enum X25519ConversionError: Swift.Error {
+    case publicKeyConversionFailed(code: Int)
+    case privateKeyConversionFailed(code: Int)
+  }
+}
+
+extension PublicKey {
+  var toX25519: X25519.PublicKey {
+    get throws {
+      var outputBuffer = Array<UInt8>(repeating: 0, count: .publicKeyLength)
+      try data.withUnsafeBytes { buffer in
+        guard let pointer = buffer.baseAddress else { return }
+        let statusCode = crypto_sign_ed25519_pk_to_curve25519(&outputBuffer, pointer)
+        guard statusCode == 0 else {
+          throw X25519.X25519ConversionError.publicKeyConversionFailed(code: Int(statusCode))
+        }
+      }
+      return X25519.PublicKey(data: Data(outputBuffer))
+    }
+  }
+}
+
+extension PrivateKey {
+  var toX25519: X25519.PrivateKey {
+    get throws {
+      var outputBuffer = Array<UInt8>(repeating: 0, count: .privateKeyLength)
+      try data.withUnsafeBytes { buffer in
+        guard let pointer = buffer.baseAddress else { return }
+        let statusCode = crypto_sign_ed25519_sk_to_curve25519(&outputBuffer, pointer)
+        guard statusCode == 0 else {
+          throw X25519.X25519ConversionError.privateKeyConversionFailed(code: Int(statusCode))
+        }
+      }
+      return X25519.PrivateKey(data: Data(outputBuffer))
+    }
+  }
+}
+
+private extension Int {
+  static let privateKeyLength: Int = 32
+  static let publicKeyLength: Int = 32
+  static let sharedSecretLength: Int = 32
+}
diff --git a/Source/TonSwift/Crypto/AES_CBC.swift b/Source/TonSwift/Crypto/AES_CBC.swift
new file mode 100644
index 0000000..27e19c1
--- /dev/null
+++ b/Source/TonSwift/Crypto/AES_CBC.swift
@@ -0,0 +1,65 @@
+import Foundation
+import CommonCrypto
+
+public struct AES_CBC {
+  enum Error: Swift.Error {
+    case encryptionError(status: CCCryptorStatus)
+    case decryptionError(status: CCCryptorStatus)
+  }
+  
+  public let key: Data
+  public let iv: Data
+  
+  public init(key: Data,
+              iv: Data) {
+    self.key = key
+    self.iv = iv
+  }
+  
+  public func decrypt(cipherData: Data) throws -> Data {
+    var outputBuffer = Array<UInt8>(repeating: 0, count: cipherData.count + kCCBlockSizeAES128)
+    var numBytesDecrypted = 0
+    
+    let status = CCCrypt(CCOperation(kCCDecrypt),
+                         CCAlgorithm(kCCAlgorithmAES),
+                         CCOptions(kCCOptionPKCS7Padding),
+                         Array(key),
+                         kCCKeySizeAES256,
+                         Array(iv),
+                         Array(cipherData),
+                         cipherData.count,
+                         &outputBuffer,
+                         outputBuffer.count,
+                         &numBytesDecrypted)
+    
+    guard status == kCCSuccess else {
+      throw Error.decryptionError(status: status)
+    }
+    
+    let outputBytes = outputBuffer.prefix(numBytesDecrypted)
+    return Data(outputBytes)
+  }
+  
+  public func encrypt(data: Data) throws -> Data {
+    var outputBuffer = Array<UInt8>(repeating: 0, count: data.count + kCCBlockSizeAES128)
+    var numBytesEncrypted = 0
+    
+    let status = CCCrypt(CCOperation(kCCEncrypt),
+                         CCAlgorithm(kCCAlgorithmAES),
+                         CCOptions(kCCOptionPKCS7Padding),
+                         Array(key),
+                         kCCKeySizeAES256,
+                         Array(iv),
+                         Array(data),
+                         data.count,
+                         &outputBuffer,
+                         outputBuffer.count,
+                         &numBytesEncrypted)
+    
+    guard status == kCCSuccess else {
+      throw Error.encryptionError(status: status)
+    }
+    let outputBytes = outputBuffer.prefix(numBytesEncrypted)
+    return Data(outputBytes)
+  }
+}
diff --git a/Source/TonSwift/Crypto/HMAC_SHA512.swift b/Source/TonSwift/Crypto/HMAC_SHA512.swift
new file mode 100644
index 0000000..08db66b
--- /dev/null
+++ b/Source/TonSwift/Crypto/HMAC_SHA512.swift
@@ -0,0 +1,28 @@
+import Foundation
+import CommonCrypto
+
+public struct HMAC_SHA512 {
+  public static func hmacSha512(message: Data, key: Data) -> Data {
+    let count = Int(CC_SHA512_DIGEST_LENGTH)
+    var outputBuffer = Array<UInt8>(repeating: 0, count: count)
+    
+    key.withUnsafeBytes { bufferPointer in
+      guard let keyPointer = bufferPointer.baseAddress else { return }
+      message.withUnsafeBytes { bufferPointer in
+        guard let messagePointer = bufferPointer.baseAddress else { return }
+        CCHmac(
+          CCHmacAlgorithm(
+            kCCHmacAlgSHA512
+          ),
+          keyPointer,
+          key.count,
+          messagePointer,
+          message.count,
+          &outputBuffer
+        )
+      }
+    }
+    return Data(bytes: outputBuffer, count: count)
+  }
+}
+
diff --git a/Source/TonSwift/Util/OpCodes.swift b/Source/TonSwift/Util/OpCodes.swift
index a911a71..efb0b54 100644
--- a/Source/TonSwift/Util/OpCodes.swift
+++ b/Source/TonSwift/Util/OpCodes.swift
@@ -10,4 +10,5 @@ public enum OpCodes {
   public static var LIQUID_TF_BURN: Int32 = 0x595f07bc
   public static var WHALES_DEPOSIT: Int32 = 2077040623
   public static var WHALES_WITHDRAW: UInt32 = 3665837821
+  public static var ENCRYPTED_COMMENT: Int32 = 0x2167da4b
 }
diff --git a/Source/TonSwift/Util/RandomBytes.swift b/Source/TonSwift/Util/RandomBytes.swift
new file mode 100644
index 0000000..b2cb2cb
--- /dev/null
+++ b/Source/TonSwift/Util/RandomBytes.swift
@@ -0,0 +1,20 @@
+import Foundation
+
+public struct RandomBytes {
+  public enum Error: Swift.Error {
+    case failedGenerate(statusCode: Int)
+    case other
+  }
+  
+  public static func generate(length: Int) throws -> Data {
+    var outputBuffer = Data(count: length)
+    let resultCode = try outputBuffer.withUnsafeMutableBytes {
+      guard let baseAddress = $0.baseAddress else { throw Error.other }
+      return SecRandomCopyBytes(kSecRandomDefault, length, baseAddress)
+    }
+    guard resultCode == errSecSuccess else {
+      throw Error.failedGenerate(statusCode: Int(resultCode))
+    }
+    return outputBuffer
+  }
+}
diff --git a/Tests/TonSwiftTests/CommentEncryption/CommentDecryptorTests.swift b/Tests/TonSwiftTests/CommentEncryption/CommentDecryptorTests.swift
new file mode 100644
index 0000000..85fc06f
--- /dev/null
+++ b/Tests/TonSwiftTests/CommentEncryption/CommentDecryptorTests.swift
@@ -0,0 +1,31 @@
+import XCTest
+@testable import TonSwift
+
+final class CommentEncryptionTests: XCTestCase {
+  func testA() throws {
+    let mnemonicA = Mnemonic.mnemonicNew()
+    let keyPairA = try Mnemonic.mnemonicToPrivateKey(mnemonicArray: mnemonicA)
+    
+    let mnemonicB = Mnemonic.mnemonicNew()
+    let keyPairB = try Mnemonic.mnemonicToPrivateKey(mnemonicArray: mnemonicB)
+    
+    let message = "this is the best message in the world"
+    
+    let encrypted = try CommentEncryptor(
+      comment: message,
+      senderPublicKey: keyPairA.publicKey,
+      senderPrivateKey: keyPairA.privateKey,
+      peerPublicKey: keyPairB.publicKey,
+      senderAddress: try Address.parse("0:25603f6d7d3a1c6f981f02237c917150a6f2af971e83dd9e19605fa57a5d5b00")
+    ).encrypt()
+    
+    let decrypted = try CommentDecryptor(
+      privateKey: keyPairB.privateKey,
+      publicKey: keyPairB.publicKey,
+      cipherText: encrypted.hexString(),
+      senderAddress: try Address.parse("0:25603f6d7d3a1c6f981f02237c917150a6f2af971e83dd9e19605fa57a5d5b00")
+    ).decrypt()
+    
+    XCTAssertEqual(decrypted, message)
+  }
+}