5 Questions About Encryption Use in PGP Implementation (1000 words)

There are many ways to provide encryption services. Pretty Good Privacy (PGP) is one example of an encryption package that is readily available.
Out of the 5 principal services that are provided by PGP, which services do you find the most important? Explain your answer in detail.
•Why does PGP generate a signature before adding compression?
•What is your personal opinion about PGP?
•Would you use PGP or a different encryption package? Explain your answer in detail.
•How would you implement PGP in your own company or at home?
•What are some situations where PGP would not be the best encryption package for an organization?

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I consider the encryption performed by PGP being the most important service because of the security achieved by combining the symmetric and asymmetric protocols for obtaining confidentiality and authentication. The table from Stallings’ book (page 593) is very explicit towards this matter. The message to transmit (e.g. across the network) is firstly encrypting by using CAST-128, IDEA or 3DES (symmetric algorithms) with a session key (one-time) which is generated by the sender. This symmetric key is afterwards encrypted by using either RSA or Diffie-Helman (asymmetric algorithms) together with the public key of the receiver. More than this, the hashing of the message and RSA represent a veritable digital signature method for the message. The proof of identity can’t be denied in this situation. More than this, for an attacker (eavesdropper) will be virtually impossible to recover the plaintext message by cracking all the enumerated algorithms. Not last, since it is no pattern/connection between the keys and only a small plaintext is encrypted with each key, even a partial recovery of the plaintext will not make classical attacks feasible (known plaintext related)....