The acronym CBC refers to a ciphering system called Cipher Block Chaining. This technique improves the overall security level offered by the previous ECB (Electronic CodeBlock) ciphering system by adding an additional step in the elaboration chain of data blocks. With a cryptographic system based on CBC, a non-ciphered block of data is elaborated with the XOR logical operation with the previous block which is already ciphered. Only at this time the result of the operation is "feed" into the ciphering algorithm and the procedure keeps on looping until the complete encryption of data.