With the increasing application of security systems and video surveillance systems, the security issues of video surveillance systems themselves have drawn great attention from the public and have become an urgent problem. On the official implementation of the GB35114-2017 "Public Security Video Surveillance Network Information Security Technical Requirements" standard issued by China government, the Fisec Crypto Product Engineer will introduce the new requirements of GB35114 for the password card.

It is understood that GB35114 is the first pure technical standard in China for video surveillance networking information security. According to the security protection strength, GB35114 divides the front-end equipment into three levels: A, B, and C from weak to strong, respectively. In the C-class aspect, in order to prevent video leakage and encrypt the video data, the national standard explicitly requires the symmetric cryptographic algorithm to use the SM1 and SM4 block cipher algorithm OFB mode; therefore, as a cipher card that implements functions such as storage and transmission encryption of video surveillance data. It is imperative to support the OFB model.

supporting the OFB mode is of great importance to the improvement of the security industry technical system and the improvement of the information security capability level. At present, the Fisec crypto card has fully supported the OFB mode. The video surveillance system security certification and high-speed encryption solution provided by Fisherman Information is based on commercial cryptographic technology; relying on and transforming the current security system and product architecture (back-end control and management system configuration password card, authentication service platform, etc.); combined with digital certificate Public key authentication system; implemented two-way identity authentication, data transmission and storage encryption, operation non-repudiation, information anti-tampering and other security protection functions between the front-end camera and the back-end control platform.

OFB mode means output feedback mode. It means generating a key stream by using a block cipher first, and then differentiating the key stream from the plaintext stream to obtain a ciphertext stream. The decryption process is: first generate a key stream by using a block cipher, and then XOR the key stream with the ciphertext stream to get the plaintext. This mode is very suitable for encrypting streaming data and is widely used in the encryption protection of video data.

The OFB mode is structurally similar to the CFB mode. The difference between the two modes is that the OFB mode feeds back the output of the block cipher algorithm to the shift register, while in the CFB mode, the ciphertext unit is fed back to the shift register. The encryption process of the OFB mode is defined as follows:

The OFB mode has the advantage of common stream ciphers. Besides, the OFB mode can encrypt data of any length without packet padding, and is suitable for encrypting redundant data, voice and image data, and bits errors will not be spread during transmission. For example, a 1-bit error occurs in the OFB mode C1, and only the M1 is affected in the decrypted result, and the other plaintext units are not affected. In CFB mode, its 1-bit error affects the value of each plaintext unit in the decryption result.