4. Suppose two friends Alice and Alicia are using the public key cryptosystem RSA, but are using the same modulus N in their public keys. Assume that Alice's public key is (N, e₁) and Alicia's public key is (N, e₂), where e₁ and e2 are relatively prime. Suppose that a mutual friend Bob, sends both Alice and Alicia the same message m, encrypted using their public keys. That is, Bob sends Alice the ciphertext C₁ = me₁ (mod N), and sends Alicia the ciphertext c₂ = m2 (mod N). Show that if Eve is able to intercept both the ciphertexts, she can recover the value of m.

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[Algebraic Cryptography] How do you solve this?

4.
Suppose two friends Alice and Alicia are using the public key cryptosystem RSA, but are
using the same modulus N in their public keys. Assume that Alice's public key is (N, e₁) and Alicia's public
key is (N, e₂), where e₁ and e2 are relatively prime. Suppose that a mutual friend Bob, sends both Alice
and Alicia the same message m, encrypted using their public keys. That is, Bob sends Alice the ciphertext
C₁ = m²₁ (mod N), and sends Alicia the ciphertext c₂ = m²2 (mod N). Show that if Eve is able to intercept
both the ciphertexts, she can recover the value of m.
Transcribed Image Text:4. Suppose two friends Alice and Alicia are using the public key cryptosystem RSA, but are using the same modulus N in their public keys. Assume that Alice's public key is (N, e₁) and Alicia's public key is (N, e₂), where e₁ and e2 are relatively prime. Suppose that a mutual friend Bob, sends both Alice and Alicia the same message m, encrypted using their public keys. That is, Bob sends Alice the ciphertext C₁ = m²₁ (mod N), and sends Alicia the ciphertext c₂ = m²2 (mod N). Show that if Eve is able to intercept both the ciphertexts, she can recover the value of m.
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