3rd Homework

• What is wrong with making RSA more efficient by letting one prime be smaller -- say of only 30 bits.

• How many bits should an RSA/DSA modulus / DES key have … -- for personal email? -- for business email? -- for military/classified data? -- for a CA’s signature key?

• How could one authenticate a small message … say of 50 bits using a symmetric one-time key?

• Which is a better way for Alice to send Bob an authenticated and encrypted message M?: -- EncpubkeyBob(M, SignprivkeyAlice(M)) -- EncpubkeyBob(M),SignprivkeyAlice(EncpubkeyBob(M))

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