Symmetric encryption vs Asymmetric encryption: A table to understand the differences

When it comes to encryption, there are mainly two types of play in the market: symmetric encryption and asymmetric encryption. It sounds profound, but the core difference can be summed up in one sentence - one uses the same key, while the other uses two different keys.

Core Differences: Number of Keys

Symmetric encryption is straightforward: you encrypt the information with key A, and the recipient decrypts it with key A as well. It's like you and your friend agreeing on the same password to open a safe.

Asymmetric encryption is smarter: it encrypts with a public key and decrypts with a private key. For example, if Alice wants to send a confidential message to Bob, she encrypts it with Bob's public key (which can be shared publicly), and only Bob's private key can unlock it. Even if someone intercepts the public key, it is useless, because the public key can only encrypt and cannot decrypt.

Security PK

Here is an interesting data comparison:

• Symmetric encryption: A 128-bit key can meet the basic security standard.
• Asymmetric encryption: requires a 2048-bit key to achieve the same level of security.

Why? Because there is a mathematical relationship between the two keys of asymmetric encryption, and attackers can exploit this vulnerability to try to crack it, so a longer key must be used to compensate.

Speed and Application

Symmetric encryption excels in speed — The U.S. government uses AES (Advanced Encryption Standard) to protect confidential documents. The downside is the high risk of key distribution; each recipient must receive the same key, and once it is leaked, it’s all over.

Asymmetric encryption excels in security — Email encryption and SSL/TLS protocols rely on it. The downside is poor performance, requiring more computing power.

The practical solution is a hybrid approach — Most internet communications (https) are actually a combination of two methods: first, asymmetric encryption is used to exchange symmetric keys, and then symmetric encryption is used to transmit large amounts of data. You can have both fish and bear's paws.

How is blockchain used?

There is a common misconception: many people think that Bitcoin uses asymmetric encryption. However, this is not entirely correct.

The public-private key pair of Bitcoin indeed comes from asymmetric encryption, but it uses digital signatures (ECDSA algorithm), not encryption. Signatures are used to prove that you are the true owner of the transaction, not to hide data. In simple terms, digital signature ≠ encryption; both belong to the “asymmetric encryption” family, but their purposes are different.

Summary

Symmetric vs asymmetric, there is no absolute “better”, only “more suitable”:

• Need speed? Use symmetric
• Need to securely distribute keys? Use asymmetric
• Looking for stability? Mix them up.

As new threats such as quantum computing emerge, these two systems will continue to evolve, but in the short term, they will rely on them to protect data security.