Encrypted files can be signed. Signature is to verify the integrity and authenticity of files, while encryption is to protect the confidentiality of files. Encryption and signing are two different operations, but they can be applied to files at the same time. Encrypting files can protect file contents from unauthorized access and ensure that only authorized users can decrypt and view file contents. Signature is a digital signature generated by encrypting a file with a private key, which is used to verify the integrity and authenticity of the file and ensure that the file has not been tampered with during transmission or storage.

In practical application, you can encrypt the file first, and then digitally sign the encrypted file. This not only protects the confidentiality of the file, but also verifies its integrity and authenticity. Encryption can prevent unauthorized access and theft of file contents, while signature can ensure that files are not tampered with or tampered with and detected.

It should be noted that the signature can only verify whether the file has been tampered with, but it cannot guarantee the confidentiality of the file. Therefore, while protecting files, it is necessary to comprehensively consider the use of encryption and signature, and choose appropriate measures according to specific security requirements.