Question

I have a security mechanism that implements symmetric algorithm RijndaelManaged. I managed to find information what is the maximum size of encrypted data using RijndaelManaged for particular IV. According to my calculations it will be 128 bytes. However I need to convert these 128 bytes to string using Base64. Is there a way to calculate maximum number of chars that Base64 encoding will use to encode input byte array of size 128?

Thanks,Pawel

Answer 1

Absolutely – Base64 takes 4 characters to represent every 3 bytes. (Padding is applied for binary data which isn’t an exact multiple of 3 bytes.) So 128 bytes will always be 172 characters. (The way to work this out is that base64 represents 6 bits in each character (2⁶ = 64); therefore 3 bytes = 24 bits = 4 base-64 characters.)