Why is asymmetric encryption slower than symmetric

Many messaging applications such as WhatsApp, telegram, Signal provide end-to-end encryption to provide confidentiality of the users involved and authenticate users to communicate with each other securely. In end-to-end encryption, the messages and calls are encrypted so anyone apart from the users would not obtain plaintext information.

Only the data is encrypted, but the headers, trailers, and routing information of the messages remain unencrypted. To be able to achieve this, both symmetric and asymmetric encryptions are used. Asymmetric encryption is used to initiate the conversation among the users, which involves exchanging secret keys for symmetric encryption.

After the communication is established and a secret key is exchanged, symmetric encryption is used for the whole duration of the communication. Using the public key, the sender sends an encrypted message to the receiver.

The encrypted message contains parameters to establish a symmetric session among the parties involved. The receiver would use their private key to decrypt the message and develop symmetric encryption between the sender and the receiver. The encrypted session would be recreated only when the application is re-installed, or the device is changed.

The HTTPS protocol makes it possible for website users to transmit sensitive data such as credit card numbers, banking information, and login credentials securely over the internet. For this reason, HTTPS is essential for securing online activities such as shopping, banking, and remote work. HTTPS is now the standard protocol for all websites, whether they exchange sensitive data with users. Symmetric encryption is indeed one of the fastest encryption techniques, but the secret key needs to be exchanged securely to be effective.

Asymmetric encryption is thus used to exchange the key involved for symmetric encryption. In both use cases, asymmetric encryption is used briefly to exchange parameters and establish symmetric encryption used for the rest of the communication. Being slow and resource exhaustive, asymmetric encryption is only used to cover the shortcomings of symmetric encryption. Thus, both of them are used together to achieve ideal secure communication, maintain privacy, achieve authenticity, data integrity, and proper authentication.

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Sign Up. Symmetric Vs. Asymmetric Encryption which is more Secure. Home » Encryption » Symmetric Vs. Read time: 9 minutes. Symmetric Encryption. Asymmetric Encryption. Use Cases. Symmetric Encryption Symmetric Encryption uses one key for encryption and decryption, which is why it is best used to encrypt and decrypt local data.

Some of the use cases involving symmetric encryption can be:. Data at rest: Data at rest refers to data stored in a physical drive and is not transferred among devices. This data can be stored in hard drives, SSD, flash drives, etc.

Data at rest often involves data that can be valuable to attackers as it usually contains customer information, employee information, trade secrets, Intellectual Properties, etc. To be able to protect this data adequately, organizations use symmetric encryption.

One effective way to encrypt all the data in a physical drive is to encrypt the drive itself. This is called whole disk or full disk encryption, which has fewer benefits than partial or folder encryption. Many files such as Word files create a temporary file while it is opened.

This temporary file can remain unencrypted. Many Linux distribution does provide full disk encryption while installing the operating system, and Microsoft delivers BitLocker Drive Encryption for Windows.

A new client-server session would generate new, unique session keys. Graphic: Advantages of symmetric encryption include security, speed, and industry adoption and acceptance. Symmetric encryption is used today because it can encrypt and decrypt large amounts of data quickly, and it's easy to implement. Graphic: Disadvantages of symmetric encryption include the need to ensure the security of key distribution mechanisms.

By far the biggest disadvantage of symmetric encryption is its use of a single, secret cryptographic key to encrypt and decrypt information. Well, if this secret key is stored in an insecure location on a computer, then hackers could gain access to it using software-based attacks, allowing them to decrypt the encrypted data and thereby defeating the entire purpose of symmetric encryption.

In addition, if one party or entity is encrypting at one location and a separate party or entity decrypting at a second, then the key will need to be transmitted, leaving it vulnerable to interception if the transmission channel is compromised.

The only other disadvantage to using symmetric encryption is its security efficacy when compared to asymmetric encryption, which is generally considered to be more secure but also slower to execute than symmetric encryption. Graphic: Asymmetric encryption uses public- and private-key pairs to encrypt and decrypt sensitive information. As with symmetric encryption, plaintext is still converted into ciphertext and vice versa during encryption and decryption, respectively.

The main difference is that two unique key pairs are used to encrypt data asymmetrically. Graphic: This is an illustration of the asymmetric encryption process. The same process applies when Jacqueline wants to send the file back to Claire.

Note that this is a simplification of asymmetric encryption. Like symmetric encryption, asymmetric encryption may be carried out manually or automatically. Now, do you see how asymmetric encryption could be seen as more secure than symmetric encryption? One reason asymmetric encryption is often regarded as more secure than symmetric encryption is that asymmetric encryption, unlike its counterpart, does not require the exchange of the same encrypt-decrypt key between two or more parties.

Asymmetric encryption also allows for digital signature authentication, unlike symmetric encryption. Basically, this involves using private keys to digitally sign messages or files, and their corresponding public keys are used to confirm that these messages originated from the correct, verified sender.

Published in , RSA is one of the oldest examples of asymmetric encryption. Developed by Ron Rivest, Adi Shamir, and Leonard Adleman, RSA encryption generates a public key by multiplying two large, random prime numbers together, and using these same prime numbers, generates a private key. From there, standard asymmetric encryption takes place: information is encrypted using the public key and decrypted using the private key. ECC is an RSA alternative that uses smaller key sizes and mathematical elliptic curves to execute asymmetric encryption.

ECC is much faster than RSA in terms of key and signature generation, and many consider it the future of asymmetric encryption, mainly for web traffic and cryptocurrency but for other applications as well.

Diffie-Hellman made it so that these keys could be securely exchanged over public communication channels, where third parties normally extract sensitive information and encryption keys. This is known as a TLS handshake. After the TLS handshake is complete, the client-server session keys are used to encrypt the information exchanged in that session. Graphic: Advantages of asymmetric encryption include digital signature authentication and increased security due to the privacy of decryption keys.

I mean, why would you ever choose symmetric encryption if asymmetric encryption is so secure? Graphic: Disadvantages of asymmetric encryption include slowness of execution when compared to symmetric encryption.

So, in a nutshell, symmetric encryption is faster than asymmetric encryption. Asymmetric encryption sacrifices speed for security, while symmetric encryption sacrifices security for speed.

After giving a high level explanation of the difference between secret-key encryption and public-key encryption, the book says:. So why do we bother with secret-key encryption if public-key encryption is so much easier?

Because public-key encryption is much less efficient, by several orders of magnitude. That statement really surprised me, and its not explained which leads me to believe I didn't understand the high level explanation as well as I thought.

The "moral" reason of public key encryption being slower than private key encryption is that it must realize a qualitatively harder feature: to be able to publish the encryption key without revealing the decryption key. This requires heavier mathematics, compared to symmetric encryption which is "just" making a big tangle of bits. Most known asymmetric encryption systems seem to achieve the needed security, but at some relatively heavy computational cost.

There is no proof that asymmetric encryption must really be harder, computationally-wise, than symmetric encryption, but the contrary would still be mildly surprising. Another efficiency issue with asymmetric encryption is network bandwidth. This one is an absolute limitation. Public key encryption is public: anybody, including the attacker, can use the public key to encrypt arbitrary messages.

This means that if the encryption is deterministic, then the attacker can run an exhaustive search on the encrypted data i.

The data which is encrypted is still "useful data": it has structure, it is subject to such a search. Therefore, an asymmetric encryption scheme must include extra randomness. This, in turn, necessarily implies a data size increase.

For instance, with RSA as described by PKCS 1 , with a bit key, you can encrypt a data element only up to bytes, yielding a byte value. There are many contexts where network bandwidth is a scarcer resource than CPU. Finally, there are key exchange algorithms, which are like asymmetric encryption except that you do not get to choose the "message" you send: the sender and receiver do end up with a shared secret, but that value is mostly "randomly selected".

Diffie-Hellman is the most well-known key exchange algorithm. To do "asymmetric encryption" with a key exchange algorithm involves using the "shared secret" as key in a symmetric encryption algorithm. In short, a good block cipher should "mix" the bits of the plaintext and key as thoroughly as possible, so that it becomes practically impossible to recover the key or decipher unknown ciphertext.

The thing that all these operations have in common is that they're all operations a normal CPU can perform very quickly. Hell, a Core 2 CPU can perform 6 billion of adds or xors per second!

Public-key cryptography, on the other hand, relies on the existence of trapdoor functions.