using Microsoft.Practices.EnterpriseLibrary.Security.Cryptography;
using System.Security;
using System.IO;

string exportKeyFile = @"C:keyEngagementProviderExport.txt";
string exportKeyPw = "p@ssword";
string saveKeyFile = @"C:keyEngagementProvider.key";
ProtectedKey NewServerKey;

using (FileStream fs = File.OpenRead(exportKeyFile))
{
    NewServerKey = KeyManager.RestoreKey(fs, exportKeyPw, System.Security.Cryptography.DataProtectionScope.LocalMachine);
}

using (FileStream ofs = File.OpenWrite(saveKeyFile))
{
    KeyManager.Write(ofs, NewServerKey);
}