RSA, Elliptic Curve, DSA, and Elgamal ECES Practice Questions (Page 6)

Questions 26–30

1. 26foundation · easy

   In Elgamal encryption, what does the sender compute to produce the ciphertext?

   • Ac1 = y^k mod p and c2 = m · g^k mod p
   • Bc1 = m^k mod p and c2 = y^k mod p
   • Cc1 = g^k mod p and c2 = m · y^k mod p
   • Dc1 = g^m mod p and c2 = y^m mod p
   Reveal Solution Discussion Select an answer first
2. 27foundation · easy

   In DSA verification, what is the first step after receiving the signature (r, s) and the message?

   • ADecrypt the signature using the private key
   • BCheck that 0 < r < q and 0 < s < q
   • CCompute the hash of the signature
   • DRecover the private key from the signature
   Reveal Solution Discussion Select an answer first
4. 28application · medium

   A developer is implementing ECC for a resource-constrained IoT device. The device must perform point multiplication for key exchange. Which operation is the most computationally intensive and should be optimized?

   • APoint doubling of a single point
   • BModular inversion of the point's x-coordinate
   • CPoint addition of two distinct points
   • DScalar multiplication of a point by a large integer
   Reveal Solution Discussion Select an answer first
5. 29expert · hard

   A developer is implementing ECDSA and notices that the signature generation code uses a fixed value for the ephemeral key k. Which of the following is the most serious consequence of this implementation flaw?

   • AAn attacker can recover the private key from two signatures that used the same k.
   • BThe signature will be larger than normal, causing performance issues.
   • CThe signature will be invalid because k must be a random prime.
   • DThe signature will be rejected by the verifier because k is not part of the public key.
   Reveal Solution Discussion Select an answer first
6. 30foundation · easy

   In DSA signing, what is the role of the per-message secret k?

   • AIt is the hash of the message
   • BIt is the private key used to encrypt the message
   • CIt is the public key used to verify the signature
   • DIt is a random nonce used to compute the signature component r = (g^k mod p) mod q
   Reveal Solution Discussion Select an answer first