Message Encryption is the process of encoding sent messages and documents (such as emails) so that only the intended recipient can decode and read it. This can be done with the use of encryption protocols like PGP and S/MIME. They allow for a user to generate public and private keys which are used for encryption and decryption respectively.
Message encryption performs the following functions:
– Privacy: Encryption ensures that only the person for whom the message is intended can decrypt and read it.
– Prevention of Tampering: An encoded message or document usually cannot be altered in transit. However, the use of some types of encryption algorithm renders messages susceptible to tampering.
A Digital Signature is a way of providing authenticity to messages and digital documents. It is the digital equivalent of physically signing a letter or a document. It has the following functions:
– Authentication of Emails and Documents: Digital signatures allow the recipient of a message or document to verify the sender. A digital signature is specific for a particular user and thus, a valid digital signature is used to affirm that a message originated from a specific user. This is useful in situations where very sensitive and important information is the content of such a document or message. It is also helpful in verifying the sender when the content of a message is in doubt or seems inaccurate to the recipient.
– Detection of Tampering: A digitally signed message or document cannot be altered without invalidating the signature. This is true whether the message is encrypted or not. A valid digital signature upon receipt of a message or document confirms that the message or document was not altered in transit.
– Non-repudiation: Since a digital signature is the equivalent of a handwritten signature, its use is taken to be a sign of acknowledgement of a message or document. Thus, if someone has digitally signed a document, he or she cannot deny such a document.
Message Encryption and Digital Signatures are Complementary
Having seen the differences between message encryption and digital signatures, the reality is that they are much more powerful when they are employed together. This is the reason why most encryption programs allow you to generate encryption keys as well as create a digital signature.
Whilst the encoding of a message prevents alteration of the message and guarantees privacy, it cannot guarantee authenticity. Some messages which have been encrypted using some forms of encryption algorithm can be altered. The person modifying the message or document does not need to be able to understand or read it to change it. A digital signature allows the recipient to detect such tampering since a message cannot be altered without invalidating the signature.
In reverse, a digitally signed message does not mean that it cannot be intercepted and read. Message encryption ensures the confidentiality of such a message.
Newer encryption software even offers an added layer of protection for your messages using a method called triple-wrapping. Here the message is signed, encrypted and signed again.