Encryption key class containing 4 keys. This class is used by SqlAeadAes256CbcHmac256Algorithm 1) root key - Main key that is used to derive the keys used in the encryption algorithm 2) encryption key - A derived key that is used to encrypt the plain text and generate cipher text 3) mac_key - A derived key that is used to compute HMAC of the cipher text 4) iv_key - A derived key that is used to generate a synthetic IV from plain text data.