IKE-PSK MD5 Hash

Technical details, regex signatures, and cracking commands for the IKE-PSK MD5 algorithm.

Regex Identification Signature:

                        ^[a-f0-9]{256}:[a-f0-9]{256}:[a-f0-9]{16}:[a-f0-9]{16}:[a-f0-9]{320}:[a-f0-9]{16}:[a-f0-9]{40}:[a-f0-9]{40}:[a-f0-9]{32}$
                    

Hashcat Command (Mode: 5300):

Not supported natively by John the Ripper

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What is IKE-PSK MD5?

The **IKE-PSK MD5** hash format is derived from the broader **Internet Key Exchange (IKE)** protocol suite, specifically within **Phase 1** of IKEv1 (RFC 2409), where it serves as a pre-shared key (PSK) authentication mechanism. Structurally, it combines a **plaintext pre-shared key** with a **derived session identifier** (often a concatenation of the initiator/respondent identities and a random nonce) to produce a **128-bit (16-byte) MD5 hash output**. This format is not a standalone cryptographic primitive but rather a legacy authentication construct, where the hash is computed as `MD5(PSK || session_data)`, and the result is compared against a precomputed value during the IKE handshake. Its primary use-case was in securing VPN tunnels and IPsec negotiations, though it has since been deprecated due to critical security flaws. The format lacks modern cryptographic safeguards like salting, key stretching, or message authentication codes (MACs), relying solely on the integrity of the MD5 hash function—an approach now considered insecure for authentication purposes.

The vulnerability of **IKE-PSK MD5** stems from fundamental flaws in MD5’s design and its application in this context. The algorithm is **collision-prone**, with known practical attacks (e.g., the **MD5 collision attack** by Wang et al., 2005) demonstrating how distinct inputs can produce identical hashes, enabling adversaries to forge valid IKE handshake messages. More critically, the absence of a **salt** or **iterated hashing** makes it susceptible to **rainbow table attacks** and **precomputed hashcat-style cracking**, as the same PSK can be reused across sessions without diversification. Additionally, the **computational efficiency** of MD5 (especially on modern GPUs via optimizations like **OpenCL/Fermi**) allows brute-force attacks to achieve **hash rates exceeding 100+ GHash/s**, rendering it impractical for securing long-term credentials. The protocol’s reliance on a **static hash comparison** further exacerbates risks, as an attacker could intercept and replay valid handshakes without ever compromising the PSK itself—only its derived hash.

Identifying IKE-PSK MD5 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 MD5, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack IKE-PSK MD5

If you need to recover the plaintext password for a IKE-PSK MD5 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.