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arxiv: 2512.15966 · v2 · pith:B6NNOKT7new · submitted 2025-12-17 · 💻 cs.CR

Charge It to My Neighbor: A Relay Attack on ISO 15118 Plug and Charge Payment

Jakob L\"ow , Vishwa Vasu , Thomas Hutzelmann , Hans-Joachim Hof This is my paper

Pith reviewed 2026-05-22 13:07 UTC · model grok-4.3

classification 💻 cs.CR
keywords ISO 15118plug and chargerelay attackelectric vehicle chargingpayment securitycryptographyTLS
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The pith

An attacker can use a fake charging station to relay ISO 15118 authentication and bill charging to a victim's contract.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper shows how the plug-and-charge feature in the ISO 15118 standard for electric vehicle fast charging can be exploited through a relay attack. The attacker connects a fake station to the victim's vehicle and forwards the cryptographic messages to a real station where their own vehicle is charging. Because the signatures do not tie the authentication to a specific station and TLS certificate checks have weaknesses, the relay goes undetected. The victim ends up paying for the attacker's electricity use. The authors implement the full attack and discuss fixes.

Core claim

We present a novel relay attack against this mechanism: an attacker builds a fake charging station, plugs it into a victim's vehicle, and relays the cryptographic authentication to a real charging station - charging the attacker's vehicle while billing the victim. The attack exploits the absence of station-identifying information in the plug-and-charge signature, combined with weaknesses in how ISO 15118 handles TLS certificates. We provide a proof-of-concept implementation demonstrating the full attack chain and discuss possible mitigations and alternatives.

What carries the argument

The relay of cryptographic authentication messages between a fake charging station connected to the victim's vehicle and a real charging station connected to the attacker's vehicle, made possible by missing station identifiers in the plug-and-charge signatures.

If this is right

  • As plug-and-charge adoption grows, this vulnerability becomes widely exploitable.
  • Attackers can obtain free charging sessions billed to unsuspecting victims.
  • Current ISO 15118 implementations require updates to prevent such relays.
  • Alternative payment mechanisms may be needed if signatures cannot be secured.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Similar relay risks may exist in other vehicle-to-grid or automated payment systems without location binding.
  • Adding station-specific data to the signed messages would likely block this attack.
  • Testing the PoC against commercial charging stations could reveal how widespread the issue is.

Load-bearing premise

The ISO 15118 plug-and-charge signatures lack station-identifying information and the TLS certificate handling contains exploitable weaknesses that permit undetected message relay between stations.

What would settle it

An implementation of ISO 15118 that includes station identity in the contract certificate signatures or enforces strict TLS certificate checks that detect relays would prevent the attack from succeeding.

Figures

Figures reproduced from arXiv: 2512.15966 by Hans-Joachim Hof, Jakob L\"ow, Thomas Hutzelmann, Vishwa Vasu.

Figure 1
Figure 1. Figure 1: Charging Communication OSI Layer Overview To initialize each layer of the charging communication, the standard consists of multiple steps for discovering the charging station, exchanging information such as encryption keys, supported protocols, and even payment information: • In the first step, low-level communication according to IEC 61851 is established [13]. This low-level com￾munication is very basic a… view at source ↗
Figure 2
Figure 2. Figure 2: SLAC sequence [4] 2.3 Service Discovery Protocol (SDP) SDP is used in ISO 15118 for exchanging addresses, ports, and connection modes. The electric vehicle sends a multicast UDP message (Service Discovery Protocol Request). The charging station responds with an SDP response message that includes the TCP port number the vehicle shall connect to [5, 14, 22]. In addition to discovering the address and port nu… view at source ↗
Figure 3
Figure 3. Figure 3: Plug and Charge Relay Attack certificates and private keys obtained from any compromised charging station to make the emulator impersonate any real charging station. 4 Implementing and Combining Vulnerabilities for a Payment Fraud Proof of Concept The previous section described a plug and charge relay vul￾nerability allowing an attacker to charge a vehicle but mak￾ing a second vehicle, the victim vehicle, … view at source ↗
Figure 4
Figure 4. Figure 4: Wireshark Log of the two charging sessions during the attack vehicle while billing the victim vehicle for the provided energy. • The compromised charging station does not actually participate in the communication during the attack, but the attacker was previously able to extract this charging station’s certificate and private key. • The fake charging station is a presumably built device. It does not need t… view at source ↗
read the original abstract

ISO 15118, the leading standard for DC fast charging in Europe, includes a plug-and-charge mechanism that allows electric vehicles to handle payment automatically via contract certificates. We present a novel relay attack against this mechanism: an attacker builds a fake charging station, plugs it into a victim's vehicle, and relays the cryptographic authentication to a real charging station - charging the attacker's vehicle while billing the victim. The attack exploits the absence of station-identifying information in the plug-and-charge signature, combined with weaknesses in how ISO 15118 handles TLS certificates. We provide a proof-of-concept implementation demonstrating the full attack chain and discuss possible mitigations and alternatives. As plug-and-charge adoption grows, addressing this vulnerability is critical before it becomes widely exploitable.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript presents a relay attack on the ISO 15118 Plug-and-Charge (PnC) payment mechanism for electric vehicle DC fast charging. An attacker deploys a fake charging station connected to a victim's vehicle and relays the cryptographic authentication and authorization messages to a legitimate charging station, enabling the attacker's vehicle to charge while the victim's contract certificate is used for billing. The attack is claimed to exploit the absence of station-identifying information in the PnC signatures and weaknesses in TLS certificate handling. A proof-of-concept implementation is provided, along with discussion of mitigations.

Significance. If the attack chain holds under realistic backend validation, the result would be significant for the security of automated EV payment systems as PnC adoption increases in Europe. The provision of a working proof-of-concept implementation is a clear strength, as it supplies concrete evidence of feasibility rather than a purely theoretical analysis. The work also usefully identifies potential protocol-level gaps that could inform future revisions to ISO 15118.

major comments (2)
  1. [§4 and §5] §4 (Attack Description) and §5 (Implementation): The central claim that the relay succeeds because 'the plug-and-charge signature contains no station-identifying information' and that the backend accepts the authorization without binding to the physical station performing the charge is load-bearing. The manuscript does not provide a concrete reference to the relevant ISO 15118 XML structures or operator backend cross-check logic that would confirm this absence; if the real station reports its own ID during the relayed session and the backend validates it against the contract certificate, the billing would fail. A detailed mapping of each relayed message to the standard's fields and an explicit statement of the assumed backend behavior are required.
  2. [§3.2] §3.2 (TLS Certificate Handling): The description of how the fake station proxies the TLS handshake and certificates does not address whether the real station's certificate chain or session parameters are forwarded in a way that would allow the backend to detect the relay. This detail is necessary to substantiate the claim of 'undetected message relay'.
minor comments (2)
  1. [Abstract and §1] The abstract and introduction would benefit from a brief comparison to prior relay attacks on other EV charging or payment protocols to better situate the novelty claim.
  2. [Figure 2] Figure 2 (attack diagram) uses overlapping arrows that reduce readability; consider separating the message flows more clearly.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable feedback on our manuscript. We appreciate the recognition of the proof-of-concept implementation as a strength. Below, we provide point-by-point responses to the major comments and outline the revisions we will make to address them.

read point-by-point responses

  1. Referee: [§4 and §5] §4 (Attack Description) and §5 (Implementation): The central claim that the relay succeeds because 'the plug-and-charge signature contains no station-identifying information' and that the backend accepts the authorization without binding to the physical station performing the charge is load-bearing. The manuscript does not provide a concrete reference to the relevant ISO 15118 XML structures or operator backend cross-check logic that would confirm this absence; if the real station reports its own ID during the relayed session and the backend validates it against the contract certificate, the billing would fail. A detailed mapping of each relayed message to the standard's fields and an explicit statement of the assumed backend behavior are required.

    Authors: We agree that additional explicit references would strengthen the presentation. In the revised version we will add a detailed mapping of the relayed messages (AuthorizationReq, AuthorizationRes, and ContractCertificate) to the precise XML elements and fields defined in ISO 15118-2. We will also state our backend assumptions explicitly: the PnC signature is generated over the contract certificate and the EV’s identification data but does not incorporate the EVSEID or any station-specific identifier; the backend therefore authorizes the session on the basis of the contract alone. Our proof-of-concept confirms that the relayed session is accepted under this model. Should individual operators add proprietary station-binding checks, that would constitute an orthogonal countermeasure outside the current standard. revision: yes

  2. Referee: [§3.2] §3.2 (TLS Certificate Handling): The description of how the fake station proxies the TLS handshake and certificates does not address whether the real station's certificate chain or session parameters are forwarded in a way that would allow the backend to detect the relay. This detail is necessary to substantiate the claim of 'undetected message relay'.

    Authors: We will expand §3.2 with a clearer description of the two independent TLS sessions. The fake station terminates the TLS connection from the victim vehicle using its own certificate and, separately, initiates a fresh TLS connection to the legitimate station using the legitimate station’s certificate. Only the ISO 15118 application-layer messages are forwarded; the real station’s certificate chain and TLS session parameters are never presented to the vehicle. Consequently the backend, which communicates exclusively with the legitimate station, observes a normal TLS handshake and certificate from that station. We will include this clarification together with a short sequence diagram in the revision. revision: yes

Circularity Check

0 steps flagged

No circularity: protocol attack demonstration with independent PoC

full rationale

The paper is a security analysis and proof-of-concept implementation of a relay attack on ISO 15118 plug-and-charge. It contains no mathematical derivations, equations, fitted parameters, predictions of quantities, or self-citations that serve as load-bearing justifications for the central claim. The attack feasibility rests on direct inspection of the protocol specification and TLS handling, plus an implemented demonstration; these are externally verifiable and do not reduce to prior results by construction within the paper itself.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the accuracy of the ISO 15118 standard specification regarding signature contents and TLS handling, plus the practical feasibility of implementing a relay in real hardware.

axioms (2)
  • domain assumption ISO 15118 plug-and-charge signatures do not contain station-identifying information.
    This is explicitly cited as the key property exploited by the relay attack.
  • domain assumption TLS certificate validation in the protocol permits relay of messages without detection.
    Combined with the signature weakness to enable the full attack chain.

pith-pipeline@v0.9.0 · 5666 in / 1320 out tokens · 61422 ms · 2026-05-22T13:07:23.147611+00:00 · methodology

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Reference graph

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