How Does PGP Encryption Work?
PGP is based on a combination of public key or asymmetric cryptography and symmetric cryptography. With asymmetric cryptography, a person has a pair of related keys. The private key is kept secret and can be used to decrypt messages and generate digital signatures. The public key is made public and can be used to encrypt messages or verify digital signatures generated with the associated private key. The main limitation of public key cryptography is that it is very slow.
For encrypting large volumes of data — like the contents of an email — it is better to use a symmetric encryption algorithm such as AES. However, symmetric encryption requires a shared secret key.
PGP uses the best of both algorithms by combining them in a single protocol. In PGP, an email is encrypted and sent via the following process:
- The sender generates a random, one-time session key for an asymmetric encryption algorithm.
- The sender compresses the email’s contents for efficiency.
- Using the asymmetric algorithm, the sender encrypts the email using the single-use session key.
- The sender encrypts the session key using the asymmetric encryption algorithm and the recipient’s public key.
- The encrypted message and encrypted session key are sent to the intended recipient.
At the other end of the communication, the recipient receives the bundle of the encrypted message and session key. They can read the message after completing the following steps:
- Decrypt the session key using their private key and the asymmetric encryption algorithm.
- Use the decrypted session key to decrypt the message with the symmetric encryption algorithm.
- Decompress the decrypted message to reveal the original message.
This process would create a message that could only be opened by the intended recipient. It is also possible to authenticate the identity of the sender of the message as well. The sender can digitally sign a message using their private key and include the signature alongside the message. The recipient can then verify the digital signature using the sender’s public key (which should be known to them).
PGP Encryption Uses
PGP is a versatile tool that takes advantage of the full capabilities of asymmetric cryptography. Some of the applications of PGP include the following:
- Email Encryption: Some encrypted email solutions, such as ProtonMail, support the use of PGP. This makes it possible to securely send emails that only the intended recipient can open.
- File Encryption: In addition to encrypting emails, PGP can encrypt files or data in general. This makes it possible to use PGP to encrypt data stored in the public cloud.
- Digital Signatures: PGP can also digitally sign data as well as encrypt it. This can help to prove the authenticity and integrity of encrypted or unencrypted data.
Benefits of PGP Encryption
PGP can be a valuable tool with several benefits, including the following:
- Data Confidentiality: PGP uses strong encryption algorithms that help to ensure that sensitive, encrypted data remains private.
- Data Integrity: The digital signature algorithms used are equally secure, providing strong authentication of the sender’s identity and that data has not been modified in transit.
Free to Use: PGP is free-to-use, making it a very cost-effective approach to email security.
Disadvantages of PGP Encryption
PGP is not a perfect solution. Some of its limitations include the following:
- Usability: PGP can be difficult to configure and use, making it less accessible to the average user.
- Key Sharing: PGP assumes that you have and trust the public key of the other party. If this is not the case, it provides no benefit.
- Bilateral Use: PGP only works if both parties are using PGP, limiting the pool of people that you can communicate with using it.
Enhancing Your Organization’s Email Security
PGP can help to improve the confidentiality, integrity, and authenticity of email communications by encrypting emails and validating the sender. However, these are not the only email threats that companies face. For example, attackers with access to a compromised email account may be able to send encrypted, digitally signed emails from a trusted account that contain malicious content.
Check Point Harmony Email and Collaboration can help to secure your organization’s email. Learn more about its capabilities in this report by Gartner. Then, see Harmony Email and Collaboration in action for yourself with a free demo.
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