Composed of a series of data blocks, blockchain is essentially a decentralized database. Each of its data blocks contains information about a network transaction, which is used to verify the validity of its information and generate the next block. To ensure the security of the blockchain operation, it’s important for developers to become cryptographic experts.

Definition of Symmetric Key Cryptography

Symmetric Key Cryptography, also known as symmetric cryptography, private key cryptography, and shared key cryptography, is the basic cryptographic algorithm in cryptography.

Symmetric encryption is mainly used to convert sensitive data or information into complex ciphertext. After receiving the ciphertext, the receiver needs to decrypt the ciphertext with the encryption key and the inverse algorithm of the same algorithm to get the readable plaintext.

As shown in the figure above, user A wants to send plaintext 1 to user B. In order to avoid leakage of information, user A encrypts the text by adding key e (or multiplying e, e power, and other complex operations) to form ciphertext 1e. After user B receives the ciphertext, he/she uses the inverse operation of the cryptography method to decrypt the ciphertext and obtain the plaintext. We call this symmetric cryptography.

Classification of Symmetric Key Cryptography

All symmetric cryptography methods share a common feature - the key used for encryption and decryption is the same. The advancement of technology has further divided symmetric cryptography methods into single ciphers and block ciphers. The latter divides plaintext into several groups for encryption, and the final encryption results depend on the specific content of each character in the same group.

Although single sequence keys only require operations on a single key T and the operation speed is much faster than block ciphers, what’s most commonly used is the block cipher. That’s because block ciphers are more secure when they’re made complex.

Common Symmetric Cryptography Standards

There are many standards for symmetric encryption algorithms, including DES, 3DES, AES, TDEA, Blowfish, and RC2, among which DES, 3DES, and AES are more common.

DES Algorithm

Released by the NBS of the United States in 1977, the DES algorithm is the earliest symmetric cryptography algorithm standard. It encrypts data in groups of 64 bits, and the key length is 56 bits. This standard cryptography method has been applied for the next 20 years, serving as the cornerstone of symmetric cryptography algorithms.

3DES Algorithm

3DES (or Triple DES) is a general term for Triple Data Encryption Algorithm (TDEA). It encrypts each piece of data three times with three different keys.

Simply put, the computing power of modern computers has been greatly improved. As a result, the key length of the original DES cipher can be easily cracked by violence. It is against such a background that 3DES comes into being. It provides a relatively simple method that applies the DES encryption algorithm three times to the data block. Though it is stronger, its corresponding operation speed also slows down. Therefore, we can say that 3DES is an encryption algorithm that transitions from DES to AES.

AES Algorithm

The AES algorithm was designed by Belgian cryptographers Joan Daemen and Vincent Rijmen. That’s why the AES algorithm is also known as the Rijndael encryption method. Currently, it is the advanced encryption standard in cryptography.

Released by the National Institute of Standards and Technology (NIST) on November 26, 2001, this standard is one of the most popular algorithms in symmetric key cryptography. Fast and of high security, it supports encryption of 128, 192, 256, and 512-bit keys.

Adopted by the US federal government at present, the AES algorithm is also a substitute for the original DES. AES has been analyzed by many parties and is widely used throughout the world.

Conclusion

Symmetric cryptography is used to encrypt a large amount of data. After several upgrades, it provides a more secure environment where data and information are transmitted safely. However, all symmetric encryption methods share a common feature, that is, the key used for encryption and decryption is the same. As a result, the security of the symmetric encryption method relies not only on the strength of the encryption algorithm itself but also on whether the key is kept in a safe place. That’s to say, only if both the sender and the receiver of the message keep the key safe, the security of data transmission can be ensured.