Encryption / Decryption
Plaintext data can be read and understood without undertaking any special measures. In simple words
the measures taken to hide information is called 'encryption'. It can be used to protect information from anyone who is not supposed to see the data even if they can view the encrypted data (which is usually just gibberish).
Naturally 'decryption' is the opposite of 'encryption' : measures taken to restore encrypted data to understandable form.
Cryptography
Cryptography is the process of using mathematics to encrypt and decrypt information. It enables you to transmit data across an unsecured network so it can be delivered to the intended recipient only.
"There are two kinds of cryptography in this world: cryptography that will stop your kid sister from reading your files, and cryptography that will stop major governments from reading your files. This book is about the latter."
--Bruce Schneier, Applied Cryptography: Protocols, Algorithms, and Source Code in C.
PGP is about this latter sort of cryptography. It can be strong or weak and is measured in the time / resources it would require to recover the plaintext. The result is a very strong cipher that is very difficult to decipher.
Public Key Cryptography
This form of encryption requires a pair of keys. A private key which resides with the user and a public key which resides on the server. The public key is associated with a user on the server allowing the user to use his/her private key to gain access to the server. Jscape Secure FTP Server has a convenient key manager allowing you to do exactly this.
PGP
PGP combines both public-key and conventional cryptography methods. PGP creates a 'session key' which is one time session key. This key is a random number generated from random movements of your mouse and the keystrokes you type. This session key uses a conventional encryption method to encrypt the plaintext data. The session key is then encrypted to the recipient's public key.
The recipient's copy of PGP uses his or her private key to recover the temporary session key, which PGP then uses to decrypt the conventionally-encrypted information.
JSCAPE Secure FTP Server includes built-in support for PGP and works with many popular PGP clients.
Creating a PGP key pair in Jscape Secure FTP Server
Navigate to 'File -> Key Manager'. Click on the OpenPGP keys tab and click on the 'Generate' button. This will bring you to the following screen :
'Real Name' : provide your full name here.
'Email' : your email address.
Click 'Ok' button. This will create the key and it will appear under the OpenPGP tab under 'File -> Key Manager'. Our next task is to generate a private/public key files form this key so they can be used with a PGP client. Select the newly generated key and click 'Generate' button. This will bring you to the following screen :
Type in the file path names and provide a password for the private key. Click on the 'Ok' button - this will save the appropriate files. Next we will use PGP 6.5.8 to encrypt a file using the keys generated in this step. This PGP client is compatible with Jscape Secure FTP Server and can be downloaded here.
After installing PGP 6.5.8 fire up 'PGP -> PGPkeys' from Start -> Menu of your system. This will bring up the following screen :
This is the public key store of the PGP 6.5.8 client. We will import the public key generated in
previous step so this client can encrypt files using that public key. Go to 'Keys->import' section and select the public key file. The 'Keys' column in the above screenshot shows the key names. The name you typed in the first screen will show up here.
Next go to 'PGP -> PGPtools' from Start -> Menu of the system. We will use the imported key to encrypt a file. Click on the encrypt button on the PGPtools GUI interface. Select the file to encrypt - this will bring you to the following screen :
Drag your public key to the Recipients section and click on the 'OK' button. This will encrypt the selected file and save a encrypted version of the file to the same location as the original file. At this point the encrypted file is ready to be uploaded to the server. A client such as AnyClient can be used to accomplish this.
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