Is there any semantic difference between predicate encryption and functional encryption?
Predicate encryption(PE) arrived as a descendant of attribute based encryption. Attribute based encryption allows the encryptor to embody a policy to the ciphertext (Ciphertext-Policy based encryption) and the receipent to receive a key from a central trusted authority according to his attributes. If the attributes do satisfy the policy then the receipent can decrypts. Another less secure version is the key-policy based encryption whereby the encryptor associates with the ciphertext the attributes that he wills a potential decryptor to have and the key of the receiver comes with the policy. Because attribute based encryption reveals the policy(KP-ABE) and the attributes(CP-ABE) predicate encryption comes to solve this by allowing the receipent to apply a predicate if he owns a secret key of that predicate.
Functional encryption(FE) As presented in the paper is a generalization of Identity based encryption, Attribute based encryption and predicate encryption. Instead of a predicate there is a function [Math Processing Error] $ f $ that evaluates the attributes of the ciphertext. At the paper the construction is given based on predicate encryption.
我的問題是FE與****PE相比提供了哪些額外功能。FE解決的PE中是否存在缺陷或安全漏洞？我從文獻中得到的直覺是，FE的貢獻是將前面提到的 3 種加密方案（IBE、ABE、PE）概括為 1 種方案（研究目的是為了在會議中接受，根本不實用），其次是領域的應用程序。我知道在PE中，如果您的密鑰 $ sk $ 讓您評估 $ 1 $ 謂詞 $ P $ 在密文上[Math Processing Error] $ c $ 然後你恢復明文，但如果使用FE $ F_{sk}(c)=1 $ 然後你在明文上學習函式的輸出。即：該功能可能是分類垃圾郵件的機器學習算法，因此您可以了解郵件是否為垃圾郵件，但不了解郵件的內容。它是否正確？
PE 是 FE 的子類。
這（來自另一個答案）是正確的。
另外，據我了解，您的類比是正確的。如果謂詞計算結果為真，PE 返回明文。另一方面，FE 返回明文的函式。
我們可以說 PE 是 FE 的子類，因為我們可以使用 FE 來實現 PE。只需使用身份功能。
你的例子 $ f $ 作為機器學習功能是 FE 可以做到而 PE 無法做到的一個例子。
**PE 是 FE 的子類。**可以在“密碼學理論：第 8 屆密碼學理論會議，TCC 2011”一書的第 256 頁上找到描述。
相關論文可通過 eprint.iacr.org 以 PDF 格式獲得：
Dan Boneh、Amit Sahai、Brent Waters