What are the differences between PGP and S/MIME?

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Let us understand the concepts of Pretty Good Privacy (PGP) and Secure/Multipurpose Internet mail extension (S/MIME) before learning the differences between them.

Pretty Good Privacy (PGP)

The full form of PGP is Pretty Good Privacy which is used to provide email with privacy, integrity and authentication.

PGP can be helpful in creating secure email messages. It sends the original data into encrypted form called unreadable ciphertext and passed to receiver where data is decrypted into original form by receiver key.

For example, consider two users Ram and Hari. Ram creates a session key to encrypt the message and he also encrypts the session key with the public key of Hari. When Hari receives the message, he decrypts the session key with his public key and decrypts the original data.

PGP uses encryption and hash algorithms like DES and MD5 for encryption. It helps in providing code conversion to convert the characters that don’t belong to the ASCII set. It converts those characters using Base-64 conversion. It allows segmentation, so data can be transmitted in a uniform manner.


The advantages of PGP are as follows −

  • It is freely available on the internet, so that anyone can be downloaded easily.

  • There is no compatible issue.

  • Information is not modified in transit because it is encrypted.

  • There is no chance of spoofing because the trust model is used for verification of sender.


The disadvantages of PGP are as follows −

  • PGP uses complex structure for encryption.

  • Both sender and receiver have the same versions of PGP.

  • Public keys and private keys have to be maintained carefully so that if lost can be recovered.

Secure/Multipurpose Internet mail extension (S/MIME)

The full form of S/MIME is Secure/Multipurpose Internet mail extension, which is used for email security. It is an extension of Multipurpose Internet mail extension (MIME). S/MIME allows you to sign digitally your emails so that only the intended receiver can receive the emails.

Cryptographic message syntax is used by S/MIME which defines the exact encoding scheme. It uses digital signatures for signing messages and public key encryption to encrypt.

To provide data integrity, signed data content type is used in which message digest is created and signed with the private key of signer. Signature, certificate and algorithm create the signed data object.

To provide privacy for the message, enveloped data content type is used in which the session key is encrypted with the public key of the receiver and encrypted contents, encrypted session keys, algorithms and certificates are encoded.


The advantages of S/MIME are as follows −

  • S/MIME is available in different modern mail agents such as MS outlook, Netscape etc.

  • It provides authenticity and protection of the message.

  • It is used for commercial or industry purposes.

  • With the help of email spoofing the Digital signature protects the.


The disadvantages of S/MIME are as follows −

  • Not all email software supports S/MIME signatures.

  • Due to the requirement of implemented certificates all users cannot take benefits of S/MIME as some users only want encryption.


The major differences between PGP and S/MIME are as follows −

PGP stands for Pretty Good Privacy.S/MIME stands for Secure/Multipurpose Internet Mail Extension.
It can be used by individuals and corporations.It is used by corporations or for commercial purposes.
PGP is a general purpose application to protect files and used for email security.S/MIME is used for email security.
Diffie Hellman digital signature is used.Elgamal digital signature is used.
PGP is a data encryption and decryption computer program that offers cryptographic privacy and authentication for internet data transmission.S/MIME provides the authentication, message integrity and non-repudiation of origin and data security services for electronic data transmission applications.
PGP was designed to eliminate security issues of text messages.S/MIME was designed to provide security for attachments and data files.
PGP products are costlier than S/MIME.S/MIME products are cheaper than PGP.
Updated on 22-Mar-2022 06:49:56