ECE 646, Midterm Exam 2
Fall 2001
Multiple-choice test
1. (1 pt) 1024-bit RSA can be securely used in the following block cipher
modes (choose as many as appropriate):
A. ECB
B. counter mode with j=8
C. CFB with j=64
D. CBC
E. OFB with j=1024
2. (1 pt) Using OAEP (Optimal Asymmetric Encryption Padding) before the
RSA encryption protects against the following attacks:
A. superencryption attack
B. encrypting a set of most likely messages with the public key, and
comparing the result with the ciphertext
C. factoring the modulus N using the General Number Field Sieve Method
D. short message attack (e=3, M<N1/3)
E. factoring the modulus N using Pollard's p-1 method
3. (1.5 pt) Match each RSA modulus N with the most efficient currently
known method of factoring a number of the given form and size:
A. N=P⋅Q, where P = 2512+1, Q - 50 decimal digit prime
B. N=P⋅Q, where P - 55 decimal digit prime, Q - 95 decimal digit prime
C. N=P⋅Q, where P - 25 decimal digit prime, Q - 175 decimal digit prime
D. N=P⋅Q, where P - 50 decimal digit prime, Q - 55 decimal digit prime
E. N=P⋅Q, where P = 2127-1, Q - 50 decimal digit prime
a. GNFS - General Number Field Sieve
b. QS - Quadratic Sieve
c. Pollard's P-1 method
d. ECM - Elliptic Curve Method
e. Cyclotomic Polynomial Method
