IKE-PSK SHA1 Hash

What is IKE-PSK SHA1?

The **IKE-PSK SHA1** hash format is derived from the broader **Internet Key Exchange (IKE) protocol suite**, specifically within **IKEv1** and **IKEv2**, where it serves as a pre-shared key (PSK) authentication mechanism. Structurally, it combines a **SHA-1-based hash** of the pre-shared secret (typically a password or symmetric key) with the **IKE identity payload** (e.g., IP address or hostname) to generate a cryptographic digest. This format is embedded in the **Authentication Header (AH) or Encapsulating Security Payload (ESP)** during Phase 1 of IKE negotiations, where mutual authentication between peers is established. The resulting hash is transmitted as part of the **Integrity Protection** mechanism, ensuring message authenticity without full key exchange. While SHA-1 itself was originally designed for digital signatures and data integrity (per RFC 3174), its application in IKE-PSK relies on the **HMAC-SHA1** variant, where the keyed-hash structure (KMAC) binds the PSK to the identity data, producing a 160-bit output. This format is critical in legacy VPN and site-to-site IPsec deployments where PSK-based authentication remains prevalent due to simplicity, though it lacks modern cryptographic rigor.

The **vulnerability of IKE-PSK SHA1** stems from fundamental flaws in SHA-1’s design and operational context. Primary weaknesses include **collision resistance degradation**: SHA-1’s 160-bit output space is now considered insecure for cryptographic purposes, with practical collision attacks (e.g., via **SHA-1S** or **SHA-1c**) demonstrating feasibility at sub-$100,000 computational cost. The absence of **salting** in IKE-PSK SHA1 exacerbates **rainbow table attacks**, as identical PSKs across deployments produce identical hashes, enabling precomputed lookup. Additionally, the **lack of key stretching** (e.g., PBKDF2 or Argon2) allows brute-force attacks to exploit modern **GPU/FPGA/ASIC acceleration** (e.g., via **Hashcat** or **John the Ripper**), with PSKs often constrained to 128-bit entropy at best. Optimizations like **parallelized hash chaining** and **memory-hard techniques** (e.g., **CUDA-accelerated SHA1**) further reduce cracking timeframes to minutes for weak passwords. Finally, the **replayability** of SHA-1 hashes—due to no temporal binding—enables offline dictionary attacks on captured IKE handshake fragments, where attackers can iteratively test PSK candidates without real-time authentication overhead. These vulnerabilities render IKE-PSK SHA1 unsuitable for modern security standards, despite its historical utility in low-resource or legacy environments.

Identifying IKE-PSK SHA1 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 IKE-PSK SHA1, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack IKE-PSK SHA1

If you need to recover the plaintext password for a IKE-PSK SHA1 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.