Blowfish Cipher uses data padding to ensure that plaintext inputs are a multiple of the block size, which is 64 bits. This is necessary because Blowfish operates on fixed-size blocks and any input not meeting this requirement would result in incomplete encryption or decryption.
Padding involves appending extra bits to the end of the plaintext until it reaches the required length. The most common method used with Blowfish is PKCS#5, where the value of each added bit equals the total number of bits added. For example, if three bits are needed, the appended sequence will be ’03 03 03′.
This process ensures every block has sufficient data for the cipher function. Without padding, the last block might contain insufficient data, leading to weak points in the encrypted output that could potentially be exploited by attackers.
