Security, Symmetric Encryption, Cryptography, Encryption.
c2 is also known but the plain text p2 is not known. Let us assume a single block and the output of the encryption block is b1 and b2. b1 will be equal to b2 as the nonce is reused. An attacker could xor the two ciphertexts together. So c1 xor c2 = p1 xor b1 xor p2 xor b2 = p1 xor p2 = known. Now