The hash function (these are often used for computing digital signatures) such as MD5 and SHA are not injective, a perfect hash function will be injective so i wonder what the answer should be.

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+15 votes

Consider the following two statements:

- A hash function (these are often used for computing digital signatures) is an injective function.
- A. encryption technique such as DES performs a permutation on the elements of its input alphabet.

Which one of the following options is valid for the above two statements?

- Both are false
- Statement (i) is true and the other is false
- Statement (ii) is true and the other is false
- Both are true

+19 votes

Best answer

+1 vote

**Option (i)** Here some asymmetrical algorithms where we apply** Hashing** (Hashing is a method used to verify data integrity).

1. RSA - named after Rivest, Shamir, and Adleman (investor)

2. Diffie-Hellman (DH)

3. ElGamal - based on the DH echange

4.Digital Signature Algorithm (DSA)- created by NSA

5. Eliptic Curve Cryptography (ECC)

Here some most popular Hashing types

1. MD5 (Message Digiest 5)

2. SHA 1

3. SHA 2

4. SHA 3

So we can correctly say it is not injective (one to one).

**Option (ii)** **DES (Digital Encryption Standard)** is part of symmetric key algorithm where we use same key to encrypt the data and decrypt the data. so calculating we perform permutation.

**Statement (ii) is true and the other is false**

–5 votes

+1

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