1. 相当好的隐私(PGP)：
PGP 是一个开源软件包，专为电子邮件安全而设计。 Phil Zimmerman 开发了它。它提供了密码学的基本或基本需求。在这多个步骤中，为了保护电子邮件，这些是，
1. Confidentiality
2. Authentication
3. Compression
4. Resemble
5. Segmentation
6. E-mail compatibility 2. 安全/多用途 Internet 邮件扩展 (S/MIME)：
S/MIME 是多用途 Internet 邮件扩展 (MIME) 的安全增强版本。在这种情况下，公钥加密用于数字签名、加密或解密电子邮件。用户获得具有受信任权限的公钥-私钥对，然后在电子邮件应用程序中适当地使用这些密钥。
PGP 和 S/MIME 的区别：
| S.NO | PGP | S/MIME |
|---|---|---|
| 1. | It is designed for processing the plain texts | While it is designed to process email as well as many multimedia files. |
| 2. | PGP is less costly as compared to S/MIME. | While S/MIME is comparatively expensive. |
| 3. | PGP is good for personal as well as office use. | While it is good for industrial use. |
| 4. | PGP is less efficient than S/MIME. | While it is more efficient than PGP. |
| 5. | It depends on user key exchange. | Whereas it relies on a hierarchically valid certificate for key exchange. |
| 6. | PGP is comparatively less convenient. | While it is more convenient than PGP due to the secure transformation of all the applications. |
| 7. | PGP contains 4096 public keys. | While it contains only 1024 public keys. |
| 8. | PGP is the standard for strong encryption. | While it is also the standard for strong encryption but has some drawbacks. |
| 9. | PGP is also be used in VPNs. | While it is not used in VPNs, it is only used in email services. |
| 10. | PGP uses Diffie hellman digital signature. | While it uses Elgamal digital signature. |