Which attack is the network vulnerable to when a stream cipher like RC4 is used twice with the same key?

The correct answer is C. ciphertext-only attack. In a ciphertext-only attack, an attacker intercepts two ciphertexts encrypted using the same key and tries to obtain information about the plaintext or the key. With two ciphertexts encrypted using the same key, an attacker can XOR the two ciphertexts together to obtain the XOR…

Submitted by anna_se· Mar 6, 2026Security Concepts

Question

Options

Aforgery attack
Bplaintext-only attack
Cciphertext-only attack
Dmeet-in-the-middle attack

How the community answered

(27 responses)

A
4% (1)
C
93% (25)
D
4% (1)

Explanation

In a ciphertext-only attack, an attacker intercepts two ciphertexts encrypted using the same key and tries to obtain information about the plaintext or the key. With two ciphertexts encrypted using the same key, an attacker can XOR the two ciphertexts together to obtain the XOR of the two plaintexts. If the attacker can guess or obtain some of the plaintext, they can use it to recover the other plaintext by XORing it with the XOR of the two ciphertexts. This can allow the attacker to obtain the key and decrypt other messages encrypted using the

Topics

#Stream cipher#RC4#Key reuse#Cryptographic attacks

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