To safely share copyrighted content in a peer-to-peer (P2P) network, several encryption technologies and measures can be used: 1. **Content encryption**: - Encrypt files before sharing. Common encryption algorithms include AES (Advanced Encryption Standard), which ensures that only users with the corresponding decryption key can access the content. 2. **Key management**: - Use a secure key management system. Encryption keys can be managed using a combination of symmetric and asymmetric encryption, such as using the RSA encryption algorithm to generate a key pair, where the private key is only kept by the content holder, while the public key can be shared with users who need to access the content. 3. **Digital watermarking**: - Embed a digital watermark in the file to identify the copyright and owner information. Even if the file is shared illegally, the watermark can help track and prove copyright ownership. 4. **Authentication and authorization**: - Authentication using digital certificates and public key infrastructure (PKI). Ensure that the user is an authorized user and verify the user's identity before downloading the content. 5. **Peer-to-Peer Encryption Protocol**: - Use secure P2P protocols for data transmission, such as TLS (Transport Layer Security) or DTLS (Datagram Transport Layer Security), to ensure the confidentiality and integrity of data during transmission. 6. **Smart Contract**: - With the support of blockchain technology, smart contracts can be used to automate and transparently manage the use of content. Only users who meet specific conditions can access or download content. 7. **Shared Access Rights**: - Manage content sharing through limited access or conditional access. For example, set time limits, usage limits, etc. 8. **Audit and Monitoring**: - Implement monitoring and auditing mechanisms to record file access and download behaviors, ensuring that each user's behavior can be tracked so that action can be taken when infringement occurs. By combining these technologies and measures, secure sharing of copyright-protected content can be achieved in P2P networks to prevent unauthorized access and use.