PDF 1.7 Level 8 (Acrobat 10 - 11) Hash

Technical details, regex signatures, and cracking commands for the PDF 1.7 Level 8 (Acrobat 10 - 11) algorithm.

Regex Identification Signature:

                        \$pdf\$5\*[5|6]\*[0-9]{3}\*[-0-9]{1,6}\*[0-9]\*[0-9]{1,4}\*[a-f0-9]{0,1024}\*[0-9]{1,4}\*[a-f0-9]{0,1024}\*[0-9]{1,4}\*[a-f0-9]{0,1024}
                    

Hashcat Command (Mode: 10700):

John the Ripper Command:

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What is PDF 1.7 Level 8 (Acrobat 10 - 11)?

The cryptographic hash format associated with **PDF 1.7 (Level 8, used in Adobe Acrobat 10–11)** is derived from the legacy **RC4-based encryption scheme** (specifically, the **AES-128 in ECB mode with RC4 for key derivation**), though its core hash component relies on **MD5** for generating the document’s integrity check (the "hash" in the PDF’s trailer dictionary). Introduced in **PDF 1.6 (Acrobat 9)** and standardized in **ISO 32000-1**, this format was designed to secure PDF files via **128-bit encryption**, where the encryption dictionary embeds a **hash of the entire document** (excluding the trailer) to verify tampering. The structure consists of a **header-metadata-body-trailer** pipeline, with the trailer containing a **cross-reference table hash (CRC-32)** and an **MD5 digest** of the document’s content stream, enabling integrity validation. However, its primary use-case—secure document transmission and restricted editing—was undermined by its reliance on weak cryptographic primitives, particularly the **RC4-derived key schedule** and **MD5’s collision susceptibility**.

The vulnerability of this format stems from **fundamental cryptographic flaws**, exacerbated by **implementation oversights and computational optimizations**. MD5’s **80-bit collision resistance** was already broken by 2005 (via **Dual_EC_DRBG backdoors** and later **SHA-1-style preimage attacks**), rendering its use in PDF 1.7’s integrity checks **practically useless** for detecting tampering. The **lack of salting** in key derivation (using a static "user password" or "owner password") allows for **rainbow table attacks** on weak passwords, while the **ECB-mode AES** (if misconfigured) enables **pattern leakage** via identical plaintext blocks. Further, the **RC4 component**—used in key derivation—suffers from **biased output streams**, enabling **side-channel attacks** and **GPU-accelerated brute-force** on short passwords (e.g., via **hashcat’s RC4 optimizations**). Additionally, the **absence of a proper key stretch** (e.g., PBKDF2 or Argon2) means password hashes can be cracked in **sub-millisecond ranges** on modern hardware, rendering the entire scheme **vulnerable to dictionary attacks** and **chosen-plaintext scenarios** where attackers manipulate encrypted content to exploit MD5’s deterministic nature.

Identifying PDF 1.7 Level 8 (Acrobat 10 - 11) Hashes

Identifying a hash blindly is often difficult because multiple algorithms can output strings of the exact same length. For example, a standard 32-character hexadecimal string could be MD5, NTLM, MD4, or LM. To definitively identify PDF 1.7 Level 8 (Acrobat 10 - 11), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack PDF 1.7 Level 8 (Acrobat 10 - 11)

If you need to recover the plaintext password for a PDF 1.7 Level 8 (Acrobat 10 - 11) hash during a penetration test or forensics investigation, you must supply the correct module ID to your cracking software. Use the exact commands provided at the top of this page to target the hash successfully.