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has-main-navigation jetpack-reblog-enabled"> <div id="page" class="site"> <a class="skip-link screen-reader-text" href="#content">Skip to content</a> <header id="masthead" class="site-header header_classes has-title-and-tagline has-menu" role="banner"> <div class="site-branding"> <p class="site-title"><a href="https://arthurvandermerwe.com/" rel="home">Cryptography & Payments</a></p> <p class="site-description"> Arthur Van Der Merwe </p> </div> <nav id="site-navigation" class="primary-navigation" role="navigation" aria-label="Main"> <button id="primary-close-menu" class="button close"> <span class="dropdown-icon close">Close <svg class="svg-icon" width="24" height="24" aria-hidden="true" role="img" focusable="false" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M12 10.9394L5.53033 4.46973L4.46967 5.53039L10.9393 12.0001L4.46967 18.4697L5.53033 19.5304L12 13.0607L18.4697 19.5304L19.5303 18.4697L13.0607 12.0001L19.5303 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class="page-title"><span class="archive-prefix">Monthly Archives: </span><span class="page-description">July 2015</span></h1> </header> <article id="post-170" class="post-170 post type-post status-publish format-standard hentry category-financial-switching tag-authorization-transaction tag-eftpos tag-transaction entry"> <header class="entry-header default-max-width"> <h2 class="entry-title"><a href="https://arthurvandermerwe.com/2015/07/31/the-refund-vulnerability-of-as2805-and-eftpos/" rel="bookmark">The Refund vulnerability of AS2805 and EFTPOS</a></h2> </header> <div class="entry-content"> <p>Transactions are normally validated, matched then processed. This is very common to ensure that requests sent to a payments switch are associated with its responses before delivering responses to a terminal. Now for all transaction types this process in true, except for refunds. Well, at least it’s not matched for most financial institutions in Australia.</p> <p>Below is a few descriptions of transactions that might be processed through a typical switch in Australia:</p> <hr /> <p> </p> <p><b>Authorization / Cash Out</b></p> <p>The Authorization transaction is typically used by a merchant to obtain the authorization of a transaction amount as a pre-approval for the purchase of goods or services later during the fulfillment process. Authorization transactions are typically submitted for authorization and then funds are held by the issuer until that transaction is captured or the authorization is reversed or expires. An example can be found with online retailers who initiate an Authorization transaction to guaranteed funding by the card issuer prior to the shipment/delivery (i.e. fulfillment) of the goods. An “Authorization” is also referred to as an Auth-Only transaction.</p> <p><b>Sale / Purchase</b></p> <p>A “Sale” transaction is used by merchants for the immediate purchase of goods or services. This transaction completes both the authorization and capture in a single transaction request. The Sale transaction is an Authorization and Capture transaction that if approved is automatically included for settlement.</p> <hr /> <p> </p> <p><b>Forced Sale</b></p> <p>A “Forced Sale” is a transaction initiated by a merchant with the intent of forcing the posting of the transaction against the customer account without receiving prior authorization by the card issuer, or receiving a voice authorization code from the merchant acquiring call center. An example would be when a merchant’s terminal is offline, requiring the purchase of goods being completed without receiving online authorization by the card issuer. Or they received a Voice Approval. In these cases the merchant would enter the transaction details and forward this Forced Sale transaction to the card issuer with the expectation of receiving funding for the goods or services rendered. A forced sale does not require a matching authorization. Forced Sales are also known as Off-Line Sales.</p> <p><b>Refund</b></p> <p>A Refund allows a merchant to refund a previously settled transaction and submit the refund for processing. Refunds are only allowed for financial transactions (Sale and Captured) and are typically limited to the original authorization amount, or a lesser amount, in some cases, multiple partial refunds up to the original transaction amount. Some systems incorporate a feature called Matched Refunds. Matched Refunds must match back to an original transaction to help control fraud. “ Refunds” are also sometimes referred to as a “Credit” transaction.</p> <p><b>Void</b></p> <p>Void transactions can reverse transactions that have been previously authorized or approved by the card issuer and are pending settlement. Merchants will only be allowed to void transactions that are in an open batch (pending settlement). Sale or Refund transactions are the most commonly voided transaction types.</p> <p><b>Capture</b></p> <p>The Capture transaction will allow merchants to capture a previously authorized transaction that is pending settlement, and submit it for clearing and settlement. An example is when online retailers who initiate an Authorization transaction to reserve funds by the card issuer prior to the shipment/delivery (i.e. fulfillment) of the goods, and then once fulfillment has been completed the transaction will be captured and submitted for settlement. A “Capture” is also referred to as a Pre-Authorization Completion transaction.</p> <hr /> <p> </p> <p>Now According to the AS2805 Specifications, The refund is not matched to the transaction during the refund authorization, and will approve by default, you need to match the Refund to an Authorization or Sale when doing settlement.</p> <p>This appears not implemented in Australia for some reason, and some financial institutions will actually admit it.</p> <p>I have tried this on a EFTPOS machine, you should try this as well. Simply do a refund on a EFTPOS terminal without doing a transaction. All you would need is a 4 digit password to access the refund function (in some cases refunds are not password protected) , these default passwords are published by the terminal manufacturers.</p> <p>In every case that I’ve tried this, the refund is processed and the funds appeared in my account. This is surely a massive risk for fraud!!!!</p> <p>Strange enough, the banks are not worried about this as the funds are tied to the merchant account, and it’s not a risk for the bank but for the Merchant. These are some clause in the contracts that absolve them from the risk.</p> <p>So if you have a EFTPOS terminal, ask for the refund function to be disabled or you could be out of pocket!</p> <p> </p> <p> </p> <div id="atatags-702045271-674233d3c9454"></div> <script> __ATA.cmd.push(function() { __ATA.initDynamicSlot({ id: 'atatags-702045271-674233d3c9454', location: 120, formFactor: '001', label: { text: 'Advertisements', }, creative: { reportAd: { text: 'Report this ad', }, privacySettings: { text: 'Privacy', } } }); }); </script> </div> <footer class="entry-footer default-max-width"> <span class="byline"><svg class="svg-icon" width="16" height="16" aria-hidden="true" role="img" focusable="false" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M15 7.5C15 9.15685 13.6569 10.5 12 10.5C10.3431 10.5 9 9.15685 9 7.5C9 5.84315 10.3431 4.5 12 4.5C13.6569 4.5 15 5.84315 15 7.5ZM16.5 7.5C16.5 9.98528 14.4853 12 12 12C9.51472 12 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19.5035 12.8518 19.5137 13.6396 18.7258L18.7266 13.6388C19.5146 12.8509 19.5043 11.5701 18.7037 10.7949L12.2025 4.5ZM8.4975 9.495C9.0484 9.495 9.495 9.0484 9.495 8.4975C9.495 7.9466 9.0484 7.5 8.4975 7.5C7.9466 7.5 7.5 7.9466 7.5 8.4975C7.5 9.0484 7.9466 9.495 8.4975 9.495Z" fill="currentColor"/></svg><span class="screen-reader-text">Tags:</span><a href="https://arthurvandermerwe.com/tag/authorization-transaction/" rel="tag">Authorization transaction</a>, <a href="https://arthurvandermerwe.com/tag/eftpos/" rel="tag">EFTPOS</a>, <a href="https://arthurvandermerwe.com/tag/transaction/" rel="tag">transaction</a></span><span class="comments-link"><svg class="svg-icon" width="16" height="16" aria-hidden="true" role="img" focusable="false" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M10.0458 15.0001L5.99998 17.697L5.99999 6.49478C5.99999 6.22141 6.2216 5.99979 6.49498 5.99978L17.505 5.99951C17.7784 5.9995 18 6.22113 18 6.49451L18 14.5046C18 14.778 17.7784 14.9996 17.505 14.9996L10.0458 15.0001ZM10.5 16.5L17.5051 16.4996C18.6069 16.4995 19.5 15.6063 19.5 14.5046L19.5 6.49451C19.5 5.39268 18.6068 4.49948 17.5049 4.49951L6.49494 4.49978C5.39315 4.49981 4.49999 5.39299 4.49999 6.49478L4.49998 18.3483C4.49998 18.9842 5.01549 19.4997 5.6514 19.4997C5.8787 19.4997 6.10091 19.4324 6.29004 19.3063L10.5 16.5Z" fill="currentColor"/></svg><a href="https://arthurvandermerwe.com/2015/07/31/the-refund-vulnerability-of-as2805-and-eftpos/#comments">3 Comments<span class="screen-reader-text"> on The Refund vulnerability of AS2805 and EFTPOS</span></a></span> </footer> </article> </main> </section> </div> <footer id="colophon" class="site-footer default-max-width" role="contentinfo" aria-label="Footer"> <div class="widget-area"> <div class="widget-column footer-widget-1"> <section id="recent-posts-4" class="widget widget_recent_entries"> <h2 class="widget-title">Recent Posts</h2><nav aria-label="Recent Posts"> <ul> 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based key injection for ATM</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/07/31/the-refund-vulnerability-of-as2805-and-eftpos/">The Refund vulnerability of AS2805 and EFTPOS</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/05/30/dukpt-explained-with-examples/">DUKPT Explained with examples</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/05/28/eftpos-initialisation-using-rsa-cryptography/">EFTPOS Initialisation using RSA Cryptography</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/05/20/atm-pin-encryption-using-3des/">ATM Pin encryption using 3DES</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/03/03/implementing-as2805-part-3-using-a-thales-9000-and-python/">Implementing AS2805 Part 6 Host to Host Encryption using a Thales 9000 and Python</a> </li> <li> <a href="https://arthurvandermerwe.com/2015/01/04/typical-cryptography-in-as2805-explained/">Typical Cryptography in AS2805 Explained</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/12/02/thales-9000-and-as2805-interchange-commands/">Thales 9000 with AS2805 Interchange & RSA EFTPOS Commands.</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/08/06/thales-key-exchange-examples-and-troubleshooting/">Thales Key Exchange Examples and Troubleshooting</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/08/06/testing-dukpt/">Testing DUKPT</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/07/06/parsing-as25058583-messages/">Parsing AS2505/8583 Messages</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/06/25/dynamic-key-exchange-models/">Dynamic Key Exchange Models</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/06/25/doing-pin-translation/">Doing PIN Translation with DUKPT</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/06/25/credit-vs-debit/">Credit vs Debit</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/06/22/as2805-standards-for-eft/">AS2805 Standards for EFT</a> </li> <li> <a href="https://arthurvandermerwe.com/2014/06/22/trace-your-atm-transactions/">Trace your ATM Transactions</a> </li> </ul> </nav></section><section id="archives-6" class="widget widget_archive"><h2 class="widget-title">Archives</h2><nav aria-label="Archives"> <ul> <li><a href='https://arthurvandermerwe.com/2020/02/'>February 2020</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2020/01/'>January 2020</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2019/02/'>February 2019</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2017/12/'>December 2017</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2017/02/'>February 2017</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2016/09/'>September 2016</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2016/07/'>July 2016</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2015/07/' aria-current="page">July 2015</a> (1)</li> <li><a href='https://arthurvandermerwe.com/2015/05/'>May 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