Figure 18.2 shows the relationship between the four services so far discussed.On the media (if necessary), a signature is generated using a hash of the plaintext is not compressed.After that, a copy (plus a signature if available) is com-pressed.Next, if privacy is necessary, block (plaintext or com-pressed compression signatures plus the old text) are encoded and added to the front of the symmetric encryption key with public key encryption.Finally, the entire block is converted to Radix-64 format.On reception, the first to be converted back from base 64 format to binary.Then, if the message is encrypted, the receiver recovers key and decrypt the message.Block as a result then extract.If the message is signed, recipients recover the hash code and compare it with its own calculation of hash code.
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