First simple approach for converting private key to keystore file.

Trust/EtherClient/EtherKeystore.swift

@@ -4,6 +4,7 @@ import Foundation
 import Geth
 import Result
 import KeychainSwift
+import CryptoSwift
 
 class EtherKeystore: Keystore {
 
@@ -204,6 +205,61 @@ class EtherKeystore: Keystore {
     func getGethAccount(for address: Address) -> GethAccount {
         return gethAccounts.filter { Address(address: $0.getAddress().getHex()) == address }.first!
     }
+    
+    func convertPrivateKeyToKeystoreFile(privateKey: String) {
+        
+        let password: Array<UInt8> = Array(privateKey.utf8)
+        let numberOfIterations = 4096
+        do {
+            // derive key
+            let salt: Array<UInt8> = Array("tkmlidnonknkqgvapjrpdcductebsozn".utf8) // TODO: create random 32 bit salt
+            let derivedKey = try PKCS5.PBKDF2(password: password, salt: salt, iterations: numberOfIterations, variant: .sha256).calculate()
+            
+            // encrypt
+            let iv: Array<UInt8> = AES.randomIV(AES.blockSize)
+            let aes = try AES(key: Array(derivedKey[..<16]), blockMode: .CBC(iv: iv), padding: .pkcs7)
+            let ciphertext = try aes.encrypt(password);
+            
+            // calculate the mac
+            let macData = Array(derivedKey[16...]) + ciphertext
+            let mac = SHA3(variant: .keccak256).calculate(for: macData)
+            
+            /* convert to JSONv3 */
+            
+            // KDF params
+            var kdfParams = [String: String]()
+            kdfParams["prf"] = "hmac-sha256"
+            kdfParams["c"] = String(numberOfIterations)
+            kdfParams["salt"] = salt.toHexString()
+            kdfParams["dklen"] = "32"
+            
+            // cipher params
+            var cipherParams = [String: String]()
+            cipherParams["iv"] = iv.toHexString()
+            
+            // crypto struct (combines KDF and cipher params
+            var cryptoStruct = [String: Any]()
+            cryptoStruct["cipher"] = "aes-128-ctr"
+            cryptoStruct["ciphertext"] = ciphertext.toHexString()
+            cryptoStruct["cipherparams"] = kdfParams
+            cryptoStruct["kdf"] = "pbkdf2"
+            cryptoStruct["mac"] = mac.toHexString()
+            
+            // encrypted key json v3
+            var encryptedKeyJSONV3 = [String: Any]()
+            encryptedKeyJSONV3["crypto"] = cryptoStruct
+            encryptedKeyJSONV3["version"] = 3
+            encryptedKeyJSONV3["id"] = 0;  // TODO: where to get ID from?
+            
+            // TODO: convert to required structure
+            
+        } catch {
+            
+            // TODO: proper error management
+            print(error)
+        }
+        
+    }
 }
 
 extension Account {