What is the block size, key size, and number of rounds used by the symmetric block cipher 3DES?

3DES, or Triple Data Encryption Standard, uses a block size of 64 bits. This means that each block of data that 3DES encrypts is 64 bits in length. The key size in the case of 3DES can be considered as 112 bits when using two unique keys and one key repeated in the encryption process, which is common in practice. This effectively leads to a larger effective key size compared to the original DES, which used a 56-bit key.

Additionally, 3DES operates using 48 rounds for encryption. The rounds are iterations of the algorithm that enhance security with each successive pass through the data, and 48 rounds are employed to increase the complexity of the encryption process significantly compared to earlier symmetric encryption techniques.

Thus, the combination of 64-bit blocks, a key size of 112 bits, and 48 rounds characterizes the operation of 3DES, making it more secure than its predecessor, the original DES.