What is differential cryptanalysis 

Differential cryptanalysis is a method used to break symmetric-key block ciphers by analyzing how differences in plaintext pairs affect the differences in ciphertext pairs. It involves:

1. **Selecting Pairs**: Choosing pairs of plaintexts with known differences.

2. **Analyzing Differences**: Observing how these differences propagate through the encryption process to produce differences in the ciphertexts.

3. **Finding Patterns**: Identifying patterns or biases in the way differences are handled, which can reveal information about the cipher's key or structure.

The technique is effective for ciphers with weak diffusion properties and was notably used to attack DES (Data Encryption Standard).