Below are some theoretical and technical background explanations, but please note that the following content is only for academic discussion and security research, and must not be used for any illegal purpose! ◇ Digital Certificate and Trust Chain Digital certificates are based on public key infrastructure (PKI) and are issued by trusted certificate authorities (CA). They contain the holder's public key, identification information, and digital signature. The verification process relies on a complete set of trust chains and digital signature mechanisms to ensure that the certificate has not been tampered with. Forging a digital certificate theoretically means: 1. Copying or forging the private key of a trusted CA so that a legitimate signature can be generated for any content; 2. Or finding a vulnerability that undermines existing digital signature schemes (such as RSA, ECDSA, etc.). ◇ Man-in-the-middle attack (MITM) and digital certificate forgery Man-in-the-middle attacks usually refer to a third party intercepting, tampering with, or even injecting information into a communication link. If an attacker can provide a digital certificate that looks legitimate but is actually forged or untrusted, it may be possible to trick the client into establishing an encrypted connection with it, thereby eavesdropping on or tampering with communication data. - If the client strictly verifies the certificate (including checking the certificate chain, revocation list, domain name matching, certificate transparency and other mechanisms), it is almost impossible to forge a digital certificate. - In some vulnerable environments, such as when the user ignores security warnings, uses a weakly configured system, or the CA system is compromised (there have been a few cases in history), attackers may exploit these vulnerabilities to carry out man-in-the-middle attacks. ◇ Actual situation and security protection 1. The existing digital signature algorithm and the choice of key length make it almost impossible to forge a digital certificate without advanced technology or major vulnerabilities; 2. Mechanisms such as certificate transparency, HSTS, and certificate pinning further improve the level of protection; 3. If an attacker can forge or tamper with a digital certificate, it is usually because there is a fundamental problem with the system or trust chain. In this case, the damage is often not limited to eavesdropping, but poses a serious threat to the security of the entire system. ◇ Summary In theory, if an attacker can break through the security protection of modern encryption technology and CA system (for example, stealing CA private key or exploiting system vulnerabilities), it is possible to forge digital certificates and implement man-in-the-middle attacks to eavesdrop on encrypted communications; but in reality, the above methods are extremely difficult for legitimate encrypted communications, and modern security mechanisms have been implemented in every link. If relevant security risks are found, measures should be taken as soon as possible to fix the vulnerabilities, and illegal implementation of such attacks is not only technically difficult, but also a serious criminal act. Once again, the above discussion is for reference only for technical research and security protection, and is strictly prohibited for any violation of laws and regulations.