Symmetric Blind Decryption with Perfect Secrecy

Figure 1

Blind decryption. Alice has obtained ciphertexts from an encryptor and is entitled to choose exactly one of those for decryption. Alice interacts with a decryptor that shares a key with the encryptor to transform the ciphertext message into a plain-text message . Neither the encryptor nor the decryptor learns the plain-text message chosen by Alice.