Question

Write a brief summary describing any encryption method not already mentioned in this chapter. In this summary, describe the history and origin of the algorithm. Compare the efficacy of this algorithm to other well-known algorithms.

Blowfish, AES, RC4, Serpent,3DES, RSA, PGP, Hashing, SHA, MD5 , Diffie–Hellman These are the method are already mentioned in this chapter.

Answer 1

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So from above question twofish is not mentioned in the list of encryption algorithm so we will discuss detailed information about twofish AALGORITHM

Twofish is a symmetric block cipher; a single key is used for encryption and decryption. Twofish has a block size of 128 bits, and accepts a key of any length up to 256 bits. (NIST required the algorithm to accept 128-, 192-, and 256-bit keys.) Twofish is fast on both 32-bit and 8-bit CPUs (smart cards, embedded chips, and the like), and in hardware. And it's flexible; it can be used in network applications where keys are changed frequently and in applications where there is little or no RAM and ROM available.

Twofish screams on high-end CPUs, and it's flexible enough for tiny smart-card CPUs. It also works well in hardware. And there are several performance trade-offs between key-setup time and encryption speed that make it unique among the AES candidates.

No other algorithm has the same flexibility in implementation: the ability to trade off key-setup time for encryption speed, and ROM and RAM for encryption speed. These options exist on 32-bit CPUs, 8-bit CPUs, and hardware.

And Twofish does this with a conservative design. We chose not to modify the basic Feistel network. We did not use data-dependent rotations, 32-bit multiplies, or any other poorly understood primitives. The key schedule is designed to resist even the nastiest of attacks. And we gave the cipher 16 rounds when we could only break five.

How Secure is Twofish?

Twofish is seen as a very secure option as far as encryption protocols go. One of the reasons that it wasn’t selected as the advanced encryption standard is due to its slower speed. Any encryption standard that uses a 128-bit or higher key, is theoretically safe from brute force attacks. Twofish is in this category.

Because Twofish uses “pre-computed key-dependent S-boxes”, it can be vulnerable to side channel attacks. This is due to the tables being pre-computed. However, making these tables key-dependent helps mitigate that risk. There have been a few attacks on Twofish, but according to its creator, Bruce Schneier, it did not constitute a true cryptanalysis. These attacks did not constitue a practical break in the cipher

AES vs. Twofish Encryption

• Neither AES nor Twofish is vulnerable to brute force attacks in any reasonable and practical scenario. Both encryption algorithms support key sizes of more than to 128 bits which is resistant to brute force attack.
• The security community has agreed upon AES-256 as the standard for protecting top-secret data rather than Twofish or any other cryptographic protocol.

Comparison of memory used

Memory used: Different encryption techniques require different memory size for implementation. This memory requirement depends on the number of operations to be done by the algorithm, key size used, initialization vectors used and type of operations. The memory used impacts cost of the system. It is desirable that the memory required should be as small as possible.

Algorithm	Memory used (KB)
DES	18.2
3DES	20.7
AES	14.7
Blowfish	9.38
RSA	31.5

Conclusion:

From the literature survey we reviewed and comparisons made with our results it can be said that every encryption has its own strength and weaknesses, almost every encryption is
breakable theoretically but we need to find which one is most suited to our need. So, from all information we got it can be said AES and TWOFISH are two best options which can
serve the purpose as these two beat rest of encryptions standards in term of speed, entropy, optimal encoding, but between them AES still has an upper hand due it is efficiency
which is more than TWOFISH.

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