Similarly, the IV is hashed by MD5.
The input string is converted into UTF-8, and then is encrypted using 128-bits or 256-bits AES in Cipher Block Chaining(CBC) with PKCS7 padding. The AES key size depends on the size of the hash for the key string. For example, if the hash is SHA2-256, 256-bits AES is used. Base64 is used for the encrypted binary.
The following code is an example of using the string encrypter in C#. The StringEncrypter class is implemented in the StringEncrypter.cs file.
/* * C# */ using Ryeol.Security.Cryptography; ... const string key = "This is a secret key."; const string iv = "This is an initialization vector."; // Creates an instance. StringEncrypter encrypter = new StringEncrypter(key, iv); // Sets the key hash algorithm. MD5 and SHA2-256 are supported. // In this case the hash size is 256 bits, AES-256 is used. encrypter.KeyHashAlgorithm = StringEncrypterKeyHashAlgorithm.SHA2_256; // Encrypts a string. string encrypted = encrypter.Encrypt("Test sample"); // Decrypts the encrypted string. string decrypted = encrypter.Decrypt(encrypted);
The following code shows how to use the string encrypter in ASP(VBScript). Since ASP doesn't support built-in AES algorithm, you need to install the RyeolStringEncrypter.dll file which is a COM dll based on XySSL 0.8.
(You also need to install the Visual C++ Redistributable for Visual Studio 2012.)
' ' ASP (VBScript) ' Const conKey = "This is a secret key." Const conIV = "This is an initialization vector." ' Creates an instance. Set objEncrypter = Server.CreateObject("Ryeol.StringEncrypter") objEncrypter.Key = conKey objEncrypter.IV = conIV ' Sets the key hash algorithm. MD5 and SHA2-256 are supported. ' In this case the hash size is 256 bits, AES-256 is used. objEncrypter.KeyHashAlgorithm = "SHA2-256" ' Encrypts a string. strEncrypted = objEncrypter.Encrypt("Test sample") ' Decrypts the encrypted string. strDecrypted = objEncrypter.Decrypt(strEncrypted)
June 7, 2013
The C# StringEncrypter has changed to create a hash implementation by using the Create method to support Windows XP.
December 10, 2012