Question

what are default values for RijndaelManaged class properties KeySize , BlockSize , FeedbackSize and Padding ?
and are default values the best too or not ?

Answer 1

Here is the parameterless constructor of Rijndeal class (RijndaelManaged inherits form that class)

protected Rijndael()
{
    this.KeySizeValue = 256;
    this.BlockSizeValue = 128;
    this.FeedbackSizeValue = this.BlockSizeValue;
    this.LegalBlockSizesValue = Rijndael.s_legalBlockSizes;
    this.LegalKeySizesValue = Rijndael.s_legalKeySizes;
}

What are the best values, that is hard to say, it depends from your usage. That’s way they are defined as properties 🙂