A new System.Security.Cryptography.SHA1CryptoServiceProvider instance, unless the default settings have been changed using the <cryptoClass> Element.
By default, this overload uses the System.Security.Cryptography.SHA1CryptoServiceProvider implementation of a hash algorithm. If you want to specify a different implementation, use the HashAlgorithm.Create(string) overload, which lets you specify an algorithm name, instead. The cryptography configuration system defines the default implementation of System.Security.Cryptography.HashAlgorithm.