Final answer:
When the data to be encrypted is not big enough to fill the block in block ciphers, padding is used to fill the remaining space. Padding adds extra bits or characters to match the block size. Different padding schemes exist, such as PKCS7 or Zero Padding, to determine the specific pattern of padding bits or characters used.
Step-by-step explanation:
When using block ciphers, if the data to be encrypted is not big enough to fill the block, a process called padding is used to fill up the remaining space. Padding adds extra bits or characters to the data before encryption to match the block size. For example, if the block size is 64 bits and the data is only 40 bits, the remaining 24 bits will be padded with additional bits.
There are different padding schemes that can be used, such as PKCS7 or Zero Padding. The padding scheme determines the specific pattern of bits or characters used for padding. These padding bits or characters are later removed during decryption.
Padding ensures that the block cipher can operate on data of any size, not just fixed-length blocks. It helps maintain the integrity and security of the encryption process.