AES Encryption in GPON: Enhancing Fiber Network Security

Why Choose AES for GPON Encryption?

In the broadcast method, all ONUs under the same OLT PON port receive the same information. How can we ensure that each ONU's data is not intercepted or decoded by others? To address this issue, encryption technology is employed to keep each ONU's data confidential.

Implementing AES Encryption in GPON Networks

Key Selection for AES Encryption

GPON systems support various encryption methods; among them, AES (Advanced Encryption Standard) is the most widely adopted due to its balance of security and performance. AES is a symmetric key encryption algorithm, meaning the same key is used for both encryption and decryption.

AES keys can be 128, 192, or 256 bits long. For instance, a 128-bit key comprises 128 binary digits, each being either 0 or 1. Every 8 bits represents one byte, so 128 bits equals 16 bytes. During the encryption process, this key encrypts 16 bytes of plaintext data.

Depending on the key length, AES is categorized into AES-128, AES-192, and AES-256. The choice of key length depends on several factors:

In GPON systems, AES-128 is commonly used as it provides a good balance of security, performance, and low latency—ideal for networks demanding high transmission efficiency.

AES Encryption Process

In GPON systems, AES encryption involves four core steps:

• 1. SubBytes: Each byte is replaced using a substitution table (S-box).

• 2. ShiftRows: Bytes in each row are shifted cyclically.

• 3. MixColumns: Data in each column is mixed using linear transformation (omitted in the final round).

• 4. AddRoundKey: Each data block is XORed with the round key.

AES stores plaintext in a 4x4 byte matrix, and the above steps constitute one round of transformation. In each round, a new round key is added. The number of transformations depends on the key length. For example, a 128-bit key requires 10 rounds:

Longer keys offer stronger encryption, making data more secure.

In GPON encryption, the data packet includes a header (basic information) and a payload (actual data). AES encrypts only the GEM (GPON Encapsulation Method) frame or fragmented payload, not the GEM frame header. After 10 rounds, the data length remains 128 bits, but it has undergone encryption and reordering.

The encrypted information is transmitted to the ONU via fiber optics. The ONU then uses the symmetric key to decrypt the plaintext. This completes one cycle of data transmission

AES Key Update Process in GPON

To enhance data security, GPON systems periodically perform AES key exchange and updates. The OLT initiates a key change request, and the ONU responds by generating a new key. This key is split into multiple parts and transmitted to the OLT over several sessions (usually three) to ensure reliability and accuracy.

Once the OLT receives the new key, it initiates the key-switching process, sending the frame number that uses the new key to the ONU (transmitted three times). The ONU then switches to the new key for the corresponding data frames, completing the key update process.

Advantages of AES Encryption in GPON

AES encryption ensures that data remains highly confidential and intact during transmission in GPON systems, effectively mitigating various potential threats. AES is a popular encryption choice due to its adaptability across various network systems:

• No Additional Latency: As a symmetric encryption algorithm, AES's four core operations can be efficiently implemented in the hardware and software. This allows AES to quickly process large data blocks without introducing significant latency, meeting the high efficiency and bandwidth requirements of GPON systems.

• High Compatibility: AES has become an international standard (FIPS PUB 197) and is widely used in various communication and data protection scenarios. Using a standardized encryption algorithm ensures compatibility between different devices and systems, simplifying design and implementation.

• High Flexibility: AES supports various key lengths (128-bit, 192-bit, and 256-bit), allowing network operators to select the appropriate key length based on specific security needs, and offering flexible security solutions.

To fully leverage the advantages of AES encryption, selecting network devices with robust security features is crucial. For example, FS OLT products utilize AES encryption technology in conjunction with multiple security protocols such as ACL, RADIUS, TACACS+, and DHCP to construct a solid security barrier, ensuring that data is effectively protected at every stage of transmission.

This multi-protocol, multi-layered security mechanism significantly enhances the integrity and confidentiality of the entire data transmission process. It achieves efficient data encryption while maintaining network stability and high performance, providing users with a reliable solution that combines high security with high performance.

Conclusion

AES encryption safeguards the upstream path in GPON, making it an indispensable component of GPON networks. As technology advances, the application of AES encryption in GPON will continue to deepen, working alongside various security mechanisms to offer users a higher level of security. As a global solutions provider, FS is committed to developing secure and efficient passive optical network solutions for you.