Encryption/Decryption Overview and Why Encrypt PDF Files

Encryption/Decryption overview

Encryption, also known as cryptography is the conversion of readable information, messages or data to a format that only the intended recipient can access. This process may not completely eliminate interference, but reduces the possibility of a would-be interceptor manipulating the plain text, to the detriment of innocent parties. In an encryption programme, the predetermined information, messages or data in plain text is encrypted using an encryption algorithm, also known as ciphertext. Once encrypted, it is unlikely for the encoded material to be manipulated, as exceptionally high-level computer skills and resources are required.

Decryption then is the process of taking the encoded text or data and converting it back to plain text using decryption algorithms. The information or message on receipt can be easily decrypted using a private key provided by the originator, to the intended recipient.

Type of keys

There are two keys used in encoding and decoding text:-

  1. Private Key
  2. Public Key

Symmetric key

The encryption and decryption algorithms are the same in Private/Symmetric keys. The same key should be used by communicating parties before they can attain reliable communication.

Asymmetric key

In Asymmetric key programmes, two keys are paired but are not identical. The public key is published for everyone to use when encrypting messages or data. The second which is the private key, however, remains only known to the recipient of the encoded data.


Encryption is used to protect data in transit from a company to various banks/institutions, via networks such as an outsourced payment transfer platform, Bluetooth devices, internet banking and mobile telephones, these also used by various other companies.

In recent times, encryption is used by many organisations to retain data, which may not immediately be needed for use, but may be requested for at any time, as necessary. With the encoded data kept on computers, laptops and other storage devices such as ‘USB flash drives’. Encrypting information or data ‘at rest’ preserves information through loss or theft of hard drives or laptops and in the event, physical security measures fail.

Recent threats to encrypted text ‘at rest’ have been cyber or cryptography attacks, encryption key attacks, integrity attacks, malicious attacks, and data destruction attacks. Data protection technologies aim to counter some of these attacks, so it is more difficult to locate, pilfer, defile or eliminate.

Verification of messages

Encrypting and decrypting of information can only be secure; to begin with, if the devices are used to operate the programme have not been tampered with. Encryption on its own can protect message confidentiality, but other techniques are still required to protect the authenticity and integrity of a message, such as a digital signature.

Data deletion

The conventional methods for erasing data from storage devises involve overwriting its entire file with patterns, which can take an enormous amount of time, depending on the volume of content. Cryptography offers a process of deleting the content almost instantly provided all data on the device is encrypted with the key stored on the same device. All the information becomes inaccessible by deleting the key code.

Why Encrypt PDF Files

So then, why protect PDF files? The reason being, that we only view on screen without the option to print the files. This is a strong measure designed to ensure that one never really gets to fully understand its abilities and shortcomings if any. The PDF file may never be successfully decrypted by a recipient, once its content has been encrypted. A free software application developed by Adobe to encrypt files will allow sending of files via the internet. The recipient may decrypt if decryption code has been availed to them, further permitting them to open, read, edit and print the file. Without the decryption key, the file remains a view only document, without the printing facility.

The two main ways to encrypt a PDF file are:-

  1. Password encryption
    • Relies on a shared password between the originator and the recipient.
  2. Public key Infrastructure (PKI) encryption
    • Provides greater protection by using cryptography and digital certificates.

Our Encrypt PDF and Decrypt PDF tools can be used to password protect PDF files using the “shared password” method, in which case the PDF file can only be viewed by someone who knows the password for the file.

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