Data Encryption Standard (DES) is insecure because of the size of the encryption key. Advanced Encryption Standard (AES) is the current NIST standard for encryption and is used in most applications. Explain the differences between the following concepts as they apply to both algorithms.
Concept
DES
AES
S-BOX
Permutation
Key Size
Full Answer Section
Permutation:
- DES: Utilizes a fixed permutation table (P-box), rearranging bits within a block to achieve diffusion.
- AES: Uses a more complex permutation layer, combining row shifts, column mixing, and byte transpositions for enhanced diffusion properties.
3. Key Size:
- DES: Key length is 56 bits, considered insufficient for modern security due to brute-force attack feasibility.
- AES: Offers three key sizes: 128, 192, and 256 bits, providing significantly stronger resistance against brute-force attacks and a longer lifespan of security.
4. Overall Structure:
- DES: Feistel network structure with 16 rounds of substitution and permutation.
- AES: Substitution-permutation network (SPN), applying multiple rounds of substitution, permutation, and XOR operations with the key.
Key Differences and Security Implications:
- Key Size: AES's larger key sizes make it significantly more secure against brute-force attacks compared to DES.
- S-BOX: AES's dynamically generated S-box adds complexity and resilience against cryptanalysis, surpassing DES's fixed S-boxes.
- Permutation: AES's more intricate permutation layer enhances diffusion properties, resulting in stronger security.
- Structure: AES's SPN structure generally offers better resistance against differential and linear cryptanalysis compared to DES's Feistel network.
Conclusion:
AES is considered the current standard for encryption due to its superior security features and ability to withstand modern attacks. DES, with its smaller key size and less robust structure, is now deemed insecure for most applications. AES's flexibility in key size, adaptive S-box, and complex permutation layer contribute to its strength and widespread adoption.