Difference between PGP and S/MIME

The security protocols PGP and S/MIME are created to secure the electronic mail facility. The primary distinction between these protocols is the type of algorithms utilized in their security mechanisms. PGP builds confidence between users by using either key rings or digital certificates. On the other hand, S/MIME makes use of digital signatures, message digests, encryption, etc.

In this article, you will learn about the difference between a PGP and S/MIME. But before discussing the differences, you must know about PGP and S/MIME with their advantages and disadvantages.

What is PGP?

PGP is an abbreviation for "Pretty Good Privacy". It is an open-source software program that is mainly designed for email security, and it was designed and developed by Phil Zimmerman. It offers the fundamental needs of cryptography. To secure the email, it employs many steps, including authentication, confidentiality, compression, email compatibility, segmentation, and reassembly. PGP includes a public key trust model and public key certificate management tools to implement and develop it.

PGP takes some steps to secure the email, and these steps are as follows:

1. Digital Signature

The message digest of the email message is generated using the SHA-1 algorithm, and the message digest is encrypted utilizing the sender's private key.

2. Compression

The email message and the digital signature are compressed together to decrease the final transit message size. The ZIP program is the best example of compression based on the Lempel-Ziv algorithm.

3. Encryption

It uses a symmetric key to encrypt the compressed form of the message obtained from the compression.

4. Digital Enveloping

The receiver's public key is utilized to encrypt the symmetric key utilized in the encryption step. A digital envelope is created by combining steps 3 and 4.

5. Base-64 Encoding

Step 4's output is Base-64 encoded, where a lot of arbitrary binary inputs are converted into printable characters.

Advantages and Disadvantages of PGP

There are various advantages and disadvantages of a PGP. Some main advantages and disadvantages of a PGP are as follows:

Advantages

1. There is no possibility of spoofing because the sender's identity is verified via the trust mechanism.
2. Everyone easily downloads it because it is publicly accessible online.
3. Its data is encrypted, so the data cannot be changed while it is being transferred.
4. There isn't a compatibility problem.

Disadvantages

1. Public and private keys must be carefully kept so that they may be recovered if lost.
2. PGP employs a complicated structure for encryption.
3. Both the sender and the receiver use the same PGP version.

What is S/MIME?

S/MIME is an abbreviation for "Secure/Multipurpose Internet Mail Extension". It is a secure enhanced variant of the MIME internet email format based on RSA Data security technology. Public key cryptography is utilized in this case to sign, encrypt, or decode the email digitally. The user obtains a public-private key pair from a trusted authority and then uses those keys appropriately with email programs. MIME replaced the SMTP protocol since it was limited to text and could only carry text messages. The user obtains a public-private key pair from a trusted authority and then uses those keys appropriately with email programs. MIME replaced the SMTP protocol since it was restricted to text, where only text messages were permitted to transmit. The restricted protocol SMTP was unable to communicate multimedia files and documents in many arbitrary forms because it employs a 7-bit ASCII representation of characters in an email message, which cannot represent special characters with values more than 127.

Structure of S/MIME

A MIME email message comprises a text message, some specific headers, and formatted text parts. Each segment may include an ASCII-encoded portion of data and the technique for decoding the data at the receiver's end. MIME headers provide the following information: MIME version, Content-ID, Content-Type, Content-Transfer-Encoding, and Content-Description.

Advantages and Disadvantages of S/MIME

There are various advantages and disadvantages of S/MIME. Some main advantages and disadvantages of S/MIME are as follows:

Advantages

1. It is available in various modern mail agents like Netscape, MS Outlook, etc.
2. It is utilized in commercial or industrial settings.
3. It ensures the message's validity and security.
4. The digital signature protects the email by using email spoofing.

Disadvantages

1. All users are unable to benefit from S/MIME due to the enforced certificate need because some users simply desire encryption.
2. All email clients do not support S/MIME signatures.

Key differences between PGP and S/MIME

Here, you will learn the various key differences between PGP and S/MIME. Some main differences between PGP and S/MIME are as follows:

1. PGP is made to process emails in plain text. In contrast, the S/MIME permits emails that also contain multimedia assets.
2. PGP is a general-purpose program that is mainly utilized for email security and file protection. On the other hand, the S/MIME is utilized for email security.
3. PGP is a computer program that encrypts and decrypts data and provides cryptographic privacy and authentication for internet data transfer. In contrast, the S/MIME offers data security features like message integrity, authentication, and non-repudiation of origin for electronic data transmission applications.
4. PGP is a less effective encryption method than S/MIME. In contrast, S/MIME is more effective than PGP.
5. There are 4096 public keys in PGP. In contrast, the S/MIME only has 1024 public keys.
6. PGP products are more expensive than S/MIME. In contrast, S/MIME products are less expensive than PGP.
7. PGP utilizes Diffie hellman's digital signature. In contrast, the S/MIME utilizes Elgamal's digital signature.
8. S/MIME is suitable for usage in the industry. On the other hand, PGP is useful for both personal and organizational purposes.
9. PGP is based on the exchange of user keys. On the other hand, the S/MIME depends on a hierarchically valid certificate for key exchange.
10. PGP is the standard for secure encryption. On the other hand, the S/MIME is a robust encryption standard with some limitations.

Head-to-head comparison between PGP and S/MIME

Here, you will learn the head-to-head comparisons between PGP and S/MIME. The main differences between PGP and S/MIME are as follows:

Conclusion

PGP may only support text-based email, whereas S/MIME may support various forms of multimedia, and both use different key exchange mechanisms.