In this form of encryption algorithm, every individual block contains 64-bit data, and three keys are used, where each key consists of 56 bits. Which is this encryption algorithm?

IDEA (International Data Encryption Algorithm) uses 64-bit blocks but employs a single 128-bit key, not three 56-bit keys.

Triple Data Encryption Standard (3DES/TDEA) operates on 64-bit data blocks and applies the DES cipher three times using three independent 56-bit keys (totaling 168 bits of key material). This triple application of DES was designed to overcome the vulnerability of single DES to brute-force attacks while maintaining backward compatibility with the original DES 64-bit block structure.

AES (Advanced Encryption Standard) uses 128-bit block sizes and supports key lengths of 128, 192, or 256 bits, not 64-bit blocks with three 56-bit keys.

MD5 is a cryptographic hash function that produces a 128-bit digest, not a block encryption algorithm, and does not use keys or operate on 64-bit data blocks in the same manner.