When a document is protected with a password or certificate, it is encrypted with 256-bit AES encryption in Cipher Block Chaining Encryption (CBC) mode. However, it is imperative to remember that when a PDF is encrypted with a password, only the contents of the files are encrypted and other PDF file properties, such as the number of objects in it and many other features are not encrypted.
Many researchers from various institutions in Germany have found that it is possible with the flaws in PDF encryption that leaves other properties such as page numbers, links, and the number of objects in a document unencrypted have made it possible for hackers and attackers to exploit the document. As a result, they can bypass add content to the encrypted file. Unfortunately, since the PDF files do not have integrity checks, the user will never be notified about the changes, which could entail a submission form function or JavaScript that shares the PDF content with the cybercriminals once it is opened.
Notwithstanding, due to the absence of integrity control in PDF formats, there are higher chances of malleability attacks. The attacker can take advantage of the lack of integrity control to alter the contents of a cipher block so long as they know the part of the plain text information that was encrypted. Regrettably, since Adobe encrypts editing permissions with the document and stores the file in unencrypted plaintext format, cyber criminals are always updated on the file size. As a result, they can maliciously employ this information to alter encrypted data and send the content to a third party. Research findings have found that most PDF files are vulnerable to direct exfiltration without the input of the user; hence every PDF file is at higher risk of malleability attacks in one way or the other.
Passwords are at greater risk of being cracked by attackers or hackers, and there is no variation when they are used together with PDF encryption. In cybersecurity, cracking passwords is a matter of not if but when depending on the password’s strength. With a more complicated password, it will take quite a long time to crack using brute-force attacks. On the other hand, weak passwords may take seconds, and the document is no longer safe. Brute force attack is not the only form of getting passwords cracked, however. Through phishing and social engineering, users can be tricked into exposing even the most secure password.
Even though it is never explicitly clear, the Adobe PDF authorization passkeys (i.e. document permissions or restrictions) do not utilize encryption. Nonetheless, it entails a set of controls that tells the applications for viewing PDF documents which areas to grey out. Many companies use these permissions to secure their files from editing and printing, but it has two main limitations. Firstly, since the permissions are not backed up by cryptography, they are quite easy to remove. There are many applications that can be used to remove Adobe PDF permissions in seconds; thus, editing and printing properties are restored faster than the user protecting the PDF may imagine. The second problem entails documents enforcements. The PDF reader application needs properties or ways to disable some functions for Adobe permissions to function and Adobe’s system naively trusts third-party PDF reader developers to implement this functionality.
Encrypting a PDF with a certificate is more secure compared to using a password, especially if one intends to share documents more securely because the recipient needs to have a private key to decrypt the document. The encryption algorithm is significant, such as AES vs. RSA and Key size-128 bit vs. 256-bit. However, the biggest concern is how it is implemented in services and apps. In Adobe PDF encryption, poor implementations of security keys may lead to a disastrous outcome. Adobe encrypted PDF files have a lot of weaknesses to be employed in safeguarding sensitive and private data. This is because they are limited in the scope of their use, and due to the higher chances of exfiltration attacks, they can never prevent sharing, editing, and printing of documents because passwords can be shared or cracked and permissions removed in a short time.
Unauthorized sharing of documents is a common problem facing individuals, businesses, institutions, and even organizations, increasing their vulnerability to cybercrimes such as ransomware attacks. If ransoms are not provided in time, private and confidential information may be leaked to third parties, which may ruin an organization’s reputation, causing business losses and legal consequences. Many people are oblivious that securing a PDF file using Adobe is never safe because a private document can still be shared and its contents edited by third parties. Users must comprehend that Adobe Acrobat is not security software – it was designed to act as a universal standard in which documents are published and shared to enhance the viewing and editing of PDF files. Inconceivably, the controls available today have been added as an afterthought and are poorly implemented.
Viewing of documents is protected with an open password which a document user can share alongside the file or just remove before doing so. Due to the Adobe Security Handler’s weaknesses, the permission passwords that supposedly should prevent unauthorized editing and printing of documents can be removed in seconds with numerous software applications, including Adobe Acrobat itself, so long as the open password is known.
In as much as encryption is a vital tool in the contemporary technological space, it is not enough to prevent the sharing of PDF files because encrypting a file only makes it impossible for people to access for those without the means of decrypting it. As a result, protecting a PDF file with a password only secures a file when it is in transit. However, immediately once a user gets access to the decryption key, or when the security key is weak, the passwords can be cracked, and third parties share the document.
