How to Generate Unique Public and Private Key via RSA

Question

I am building a custom shopping cart where CC numbers and Exp date will be stored in a database until processing  then deleted   I need to encrypt this data  obviously    I want to use the RSACryptoServiceProvider class   Here is my code to create my keys   public static void AssignNewKey        const int PROVIDER RSA FULL   1      const string CONTAINER NAME    KeyContainer       CspParameters cspParams      cspParams   new CspParameters PROVIDER RSA FULL       cspParams KeyContainerName   CONTAINER NAME      cspParams Flags   CspProviderFlags UseMachineKeyStore      cspParams ProviderName    Microsoft Strong Cryptographic Provider       rsa   new RSACryptoServiceProvider cspParams        string publicPrivateKeyXML   rsa ToXmlString true       string publicOnlyKeyXML   rsa ToXmlString false          do stuff with keys        Now the plan is to store the private key xml on a USB drive attached to the managers key chain   Whenever a manager leaves the company I want to be able to generate new public and private keys  and re-encrypt all currently stored CC numbers with the new public key    My problem is that the keys generated by this code are always the same  How would I generate a unique set of keys every time   UPDATE  My test code is below   note  the  privatekey  parameter here is the original private key  In order for the keys to be changed I need to verify that the private key is valid   In Default aspx cs  public void DownloadNewPrivateKey Click object sender  EventArgs e        StreamReader reader   new StreamReader fileUpload FileContent       string privateKey   reader ReadToEnd        Response Clear        Response ContentType    text xml       Response End        Response Write ChangeKeysAndReturnNewPrivateKey privateKey        In Crytpography cs   public static privateKey  public static publicKey  public static RSACryptoServiceProvider rsa   public static string ChangeKeysAndReturnNewPrivateKey string  privatekey         string testData    TestData       string testSalt    salt          encrypt the test data using the exisiting public key        string encryptedTestData   EncryptData testData  testSalt       try                  try to decrypt the test data using the  privatekey provided by user            string decryptTestData   DecryptData encryptedTestData   privatekey  testSalt              if the data is successfully decrypted assign new keys            if  decryptTestData    testData                        AssignNewKey                    AssignNewKey    should set  privateKey  to the newly created private key                return privateKey                    else                       return string Empty                      catch  Exception ex                return string Empty          public static void AssignParameter        const int PROVIDER RSA FULL   1      const string CONTAINER NAME    KeyContainer       CspParameters cspParams      cspParams   new CspParameters PROVIDER RSA FULL       cspParams KeyContainerName   CONTAINER NAME      cspParams Flags   CspProviderFlags UseMachineKeyStore      cspParams ProviderName    Microsoft Strong Cryptographic Provider       rsa   new RSACryptoServiceProvider cspParams     public static void AssignNewKey         AssignParameter         using  SqlConnection myConn   new SqlConnection Utilities ConnectionString                 SqlCommand myCmd   myConn CreateCommand             string publicPrivateKeyXML   rsa ToXmlString true           privateKey   publicPrivateKeyXML     sets the public variable privateKey to the new private key           string publicOnlyKeyXML   rsa ToXmlString false           publicKey   publicOnlyKeyXML     sets the public variable publicKey to the new public key           myCmd CommandText    UPDATE Settings SET PublicKey    PublicKey           myCmd Parameters AddWithValue   PublicKey   publicOnlyKeyXML           myConn Open             myComm ExecuteScalar            public static string EncryptData string data2Encrypt  string salt        AssignParameter         using  SqlConnection myConn   new SqlConnection Utilities ConnectionString                 SqlCommand myCmd   myConn CreateCommand             myCmd CommandText    SELECT TOP 1 PublicKey FROM Settings            myConn Open             using  SqlDataReader sdr   myCmd ExecuteReader                          if  sdr HasRows                                DataTable dt   new DataTable                    dt Load sdr                   rsa FromXmlString dt Rows 0   PublicKey   ToString                                          read plaintext  encrypt it to ciphertext     byte   plainbytes   System Text Encoding UTF8 GetBytes data2Encrypt   salt       byte   cipherbytes   rsa Encrypt plainbytes  false       return Convert ToBase64String cipherbytes     public static string DecryptData string data2Decrypt  string privatekey  string salt        AssignParameter         byte   getpassword   Convert FromBase64String data2Decrypt        string publicPrivateKeyXML   privatekey      rsa FromXmlString publicPrivateKeyXML          read ciphertext  decrypt it to plaintext     byte   plain   rsa Decrypt getpassword  false       string dataAndSalt   System Text Encoding UTF8 GetString plain       return dataAndSalt Substring 0  dataAndSalt Length - salt Length

User · Answer

The RSACryptoServiceProvider CspParameters  constructor creates a keypair which is stored in the keystore on the local machine  If you already have a keypair with the specified name  it uses the existing keypair   It sounds as if you are not interested in having the key stored on the machine   So use the RSACryptoServiceProvider Int32  constructor   public static void AssignNewKey        RSA rsa   new RSACryptoServiceProvider 2048      Generate a new 2048 bit RSA key      string publicPrivateKeyXML   rsa ToXmlString true       string publicOnlyKeyXML   rsa ToXmlString false          do stuff with keys        EDIT   Alternatively try setting the PersistKeyInCsp to false   public static void AssignNewKey        const int PROVIDER RSA FULL   1      const string CONTAINER NAME    KeyContainer       CspParameters cspParams      cspParams   new CspParameters PROVIDER RSA FULL       cspParams KeyContainerName   CONTAINER NAME      cspParams Flags   CspProviderFlags UseMachineKeyStore      cspParams ProviderName    Microsoft Strong Cryptographic Provider       rsa   new RSACryptoServiceProvider cspParams        rsa PersistKeyInCsp   false       string publicPrivateKeyXML   rsa ToXmlString true       string publicOnlyKeyXML   rsa ToXmlString false          do stuff with keys

User · Answer

When you use a code like this   using  var rsa   new RSACryptoServiceProvider 1024           Do something with the key          Encrypt  export  etc       NET  actually Windows  stores your key in a persistent key container forever  The container is randomly generated by  NET  This means    Any random RSA DSA key you have EVER generated for the purpose of protecting data  creating custom X 509 certificate  etc  may have been exposed without your awareness in the Windows file system  Accessible by anyone who has access to your account  Your disk is being slowly filled with data  Normally not a big concern but it depends on your application  e g  it might generates hundreds of keys every minute     To resolve these issues   using  var rsa   new RSACryptoServiceProvider 1024        try               Do something with the key             Encrypt  export  etc          finally            rsa PersistKeyInCsp   false           ALWAYS

User · Answer

What I ended up doing is create a new KeyContainer name based off of the current DateTime  DateTime Now Ticks ToString    whenever I need to create a new key and save the container name and public key to the database  Also  whenever I create a new key I would do the following   public static string ConvertToNewKey string oldPrivateKey            get the current container name from the database         rsa PersistKeyInCsp   false      rsa Clear        rsa   null       string privateKey   AssignNewKey true      create the new public key and container name and write them to the database               re-encrypt existing data to use the new keys and write to database         return privateKey    public static string AssignNewKey bool ReturnPrivateKey        string containerName   DateTime Now Ticks ToString            create the new key            saves container name and public key to database            and returns Private Key XML      before creating the new key

[c#] How to Generate Unique Public and Private Key via RSA

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