MPPSC 2020 Prelims Paper-I · Question 94 of 100

Correct — A, Symmetric Encryption Algorithm. Blowfish is a symmetric-key block cipher (designed by Bruce Schneier in 1993): the same secret key is used to both encrypt and decrypt the data.

• (b)Hashing Algorithm — Hashing algorithms (e.g. SHA, MD5) produce fixed-length digests and are one-way; Blowfish is a reversible cipher.
• (c)Digital Signature Algorithm — DSA is for signatures using key pairs; Blowfish is a symmetric block cipher, not a signature scheme.
• (d)Asymmetric Encryption Algorithm — Asymmetric algorithms (e.g. RSA) use separate public/private keys; Blowfish uses a single shared key (symmetric).

Encryption is either symmetric (one shared key for encrypt and decrypt — e.g. Blowfish, AES, DES) or asymmetric (a public/private key pair — e.g. RSA). Blowfish is a fast, unpatented symmetric block cipher.

Classify the algorithm: Blowfish -> symmetric block cipher. Contrast with RSA (asymmetric) and SHA (hash).

• Blowfish is a symmetric-key block cipher (Bruce Schneier, 1993).
• The same key encrypts and decrypts.
• Symmetric examples: Blowfish, AES, DES; asymmetric: RSA, ECC.
• Blowfish uses a 64-bit block and a variable-length key.

• Confusing symmetric ciphers with asymmetric ones (RSA)
• Treating a cipher as a hashing algorithm

Algorithm classification — Blowfish = symmetric encryption.

No directly related past PYQ was found.

• practice — not a real PYQ

  Which of the following is an asymmetric (public-key) encryption algorithm?

  • (a)RSA
  • (b)Blowfish
  • (c)AES
  • (d)DES

  Answer(a) RSA.

• practice — not a real PYQ

  Which of these is a hashing algorithm (not encryption)?

  • (a)SHA-256
  • (b)Blowfish
  • (c)AES
  • (d)RSA

  Answer(a) SHA-256.