Question

Which of the following statement correctly differentiates substitution and transposition ciphers ?

• A. Substitution changes the order of symbols; transposition replaces symbol
• B. Both change symbol order and values simultaneously
• C. Substitution replaces symbol with others; transposition rearranges their position
• D. Substitution is always weaker than transposition in modern cryptography

Hint:

Think of it this way: Substitution is like a Costume Party (same person, different look). Transposition is like Musical Chairs (same people, different seats).

Answer 1

The Correct Option is C

Substitution and Transposition are the two fundamental building blocks of classical ciphers. 1. Substitution Ciphers: In a substitution cipher, the identity of the characters is changed, but their positions remain the same. For example, in a Caesar cipher, 'A' might become 'D'. The core concept is replacing one symbol with another. 2. Transposition Ciphers: In a transposition cipher, the identity of the characters remains the same, but their positions are shifted. For example, "HELLO" might become "LLEHO". The core concept is rearranging or permuting the existing symbols. 3. Comparing the Options: Option (3) accurately captures these definitions: Substitution = Replacement, Transposition = Rearrangement. Option (1) is the exact opposite of the truth.