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@Thorium
Created March 4, 2012 10:39
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Decrypting a Rijndael string
open System.IO
open System.Security.Cryptography
open System.Text
open System.Diagnostics.Contracts
let DeCryptStringWith (crypted:string) (key:string) (iv:string) =
let enc = new ASCIIEncoding()
let algo = Rijndael.Create()
if(crypted.Length < 5) then
failwith "Crypted string length has to be over 5 chars."
use decrypted = new MemoryStream()
use decode = new FromBase64Transform()
let errdesc = "Failure when decrypting the string " + crypted.[0..3] + "...\r\n"
try
use decryptor = algo.CreateDecryptor(enc.GetBytes(key), enc.GetBytes(iv))
use tmpcrypt = new CryptoStream(decrypted, decryptor, CryptoStreamMode.Write)
use decodestream = new CryptoStream(tmpcrypt, decode, CryptoStreamMode.Write)
let cryptedbytes = enc.GetBytes(crypted);
decodestream.Write(cryptedbytes, 0, cryptedbytes.Length);
decodestream.Close() // lazy, has to close explicitly before use. using is not enough.
with
| :? CryptographicException as ex -> failwith(errdesc + ex.ToString())
| :? System.FormatException as ex -> failwith(errdesc + ex.ToString())
enc.GetString(decrypted.ToArray())
(*[omit:(Function to read registry keys omitted)]*)
let REGISTRYSOFTWARE = "Software";
let REGISTRYMYPATH = "MySoftware";
let GetRegistryValue key =
use path1 = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(REGISTRYSOFTWARE)
match path1 with
| null -> failwith("Access failed to registry: hklm\\"+REGISTRYSOFTWARE)
| keyhklmsw ->
use path2 = keyhklmsw.OpenSubKey(REGISTRYMYPATH)
match path2 with
| null -> failwith("Access failed to registry: " + REGISTRYMYPATH)
| keyhklmswmypath ->
match keyhklmswmypath.GetValue(key, null) with
| null -> failwith("Path not found: " + key)
| gotkey -> gotkey(*[/omit]*)
// I recommend to get key and iv from registry
// and then make one more method like:
let internal DeCryptString crypted =
let key = GetRegistryValue("rgbKey").ToString()
let iv = GetRegistryValue("rgbIV").ToString()
DeCryptStringWith crypted key iv
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