What is a serious security risk if the same per-message nonce k is reused in two DSA signatures?

The signatures become identical

The private key can be recovered from the two signatures

A cryptographer is reviewing an Elgamal signature scheme. The scheme uses a hash of the message H(m) and a random ephemeral key k. Which condition must hold for the signature to be generated correctly?

k must be equal to the private key x

k must be relatively prime to p-1

A security engineer is generating an RSA key pair for a legacy system that only supports a 512-bit modulus. The engineer wants to reduce the risk of factorization attacks. Which approach is the most effective within the constraint of the 512-bit modulus?

Select two random 256-bit primes that are not close to each other.

Use a 512-bit modulus but with a strong random number generator for prime selection.

Replace RSA with an elliptic curve algorithm that provides equivalent security with a smaller key size.

Use a larger public exponent, such as 65537, to increase encryption strength.

The security of Elgamal signatures is based on which hard mathematical problem?

The elliptic curve discrete logarithm problem

The integer factorization problem

EC-CouncilCertified Encryption Specialist

Domain 3Objective 2

RSA, Elliptic Curve, DSA, and Elgamal ECES Practice Questions (Page 8)

Part of the Asymmetric Cryptography and Number Theory domain, which makes up ~17% of our current practice bank. EC-Council does not publish an official question count, but from its 120-minute exam (~50–80 total, ~9–14 in this domain), expect 3–5 from this objective — we provide 43 practice questions to prepare you well beyond it. (estimate)

43questions here

9free pages

11concepts

Questions 36–40

36foundation · easy
What is a serious security risk if the same per-message nonce k is reused in two DSA signatures?
Select an answer first
37application · medium
A cryptographer is reviewing an Elgamal signature scheme. The scheme uses a hash of the message H(m) and a random ephemeral key k. Which condition must hold for the signature to be generated correctly?
Select an answer first
38application · medium
A security engineer is generating an RSA key pair for a legacy system that only supports a 512-bit modulus. The engineer wants to reduce the risk of factorization attacks. Which approach is the most effective within the constraint of the 512-bit modulus?
Select an answer first
39foundation · easy
The security of Elgamal signatures is based on which hard mathematical problem?
Select an answer first
40foundation · easy
Which RSA attack becomes possible when the same modulus n is shared by multiple users with different public exponents?
Select an answer first

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