Shellshock without the Shellac

A post by our exploit-herder in residence, Jason Royes

The Problem

Have you heard about Shellshock? If not, you may be living under a rock. To summarize:

If an application sets an environment variable name or value to a value that is derived from user input and subsequently executes bash (and possibly other shells), an attacker may be able to execute arbitrary code.


When I first read the post from Robert Graham, my first thought was: “when did we begin storing function definitions in environment variables?” I scanned through the section of the bash manual dedicated to environment variables and could not find anything on the topic.

I knew I was not alone after googling and finding this on Stack Overflow. Luckily, I had an old VM handy that I never update.

Here’s bash:

$ bash --version
GNU bash, version 4.2.24(1)-release (i686-pc-linux-gnu)

So, according to the stack overflow article, what’s actually going on is that bash stores exported functions in the environment.

$ f1
f1: command not found

Let us create a file that will define a function and export it:

$ cat
#! /bin/bash

f1() {
echo "in f1"

export -f f1

Now to include it:

$ source

Voila, f1 is now defined within the shell environment.

$ env|grep -A1 f1
f1=() {  echo "in f1"

If you’ve already read about the Shellshock attack, the value of f1 above should look familiar.

Bash 4.2 and Exported Functions

Bash 4.2 (vulnerable) processes environment variables in initialize_shell_variables (see variables.c). What happens when an environment variable has a value that begins with “() {“? A new buffer is allocated and the variable name is concatenated with the variable’s value. This basically creates a normal bash function declaration. The concatenated string is then evaluated with parse_and_execute:

temp_string = (char *)xmalloc (3 + string_length + char_index);

strcpy (temp_string, name);
temp_string[char_index] = ' ';
strcpy (temp_string + char_index + 1, string);

parse_and_execute (temp_string, name, SEVAL_NONINT|SEVAL_NOHIST);

Imagine an exported function named f1 that has a value resembling “() { ls -l; }”. The code above combines the name and value into temp_string, resulting in “f1() { ls -l; }”. This string is then evaluated and a function definition is burnt in memory.

The vulnerability arises because user input is being evaluated directly with the same function used to evaluate all other bash commands. If commands are appended to the end of the function definition, ex. “() { ls -l; }; ps”, they are executed. This is because they fall outside the bounds of the function declaration and so are treated just like they would be in a regular bash script. Note that anything inside the function declaration should not be executed unless the function is invoked.

The construction of temp_string also means an attacker can inject through the environment variable name. For example:

$ ./
total 6868
drwxrwxr-x 12 user1 user1    4096 Feb 13 17:28 bash-4.2
-rw-rw-r--  1 user1 user1 7009201 Feb 13  2011 bash-4.2.tar.gz
-rw-rw-r--  1 user1 user1      52 Feb 13 16:19
-rw-rw-r--  1 user1 user1      49 Feb 13 16:47
-rwxrwxr-x  1 user1 user1     101 Feb 13 17:30
-rwxrwxr-x  1 user1 user1      96 Feb 13 16:58
Segmentation fault

Whoops! Bonus segfault. Here’s

#! /usr/bin/python
import os

os.putenv('ls -l;a', '() { echo "in f2"; };')
os.system('bash -c f2')

Bash 4.3 and Exported Functions

The bash patch seems fairly concise. The patch now includes a check to make sure the variable name only contains legal characters (thwarting injection through name). There’s also a new flag called SEVAL_FUNCDEF. If parse_and_execute parses a command that is not a function definition and this flag is set, an error condition results.

This seems to correct the issue, however, relying on the function parsing code still feels dicey.

Perhaps there are other ways around these new defenses yet to be revealed.

Blackhat USA Multipath TCP Tool Release & Audience Challenge

We hope everyone found something interesting in our talk today on Multipath TCP.

We’ve posted the tools and documents mentioned in the talk at:

Update: We’ve now also added the slides from the talk.

At the end we invited participants to explore MPTCP in a little more depth via a PCAP challenge.

Without further ado, here’s the PCAP: neohapsis_mptcp_challenge.pcapng

It’s a simple scenario: one MPTCP-capable machine sending data to another. The challenge is “simply” to reassemble and recover the original data. The data itself is not complex so you should be able to tell if you’re on the right track, but getting it exactly right will require some understanding of how MPTCP works.

If you think you have it, tweet us and follow us (@secvalve and @coffeetocode) and we’ll PM you to check your solution. You can also ask for questions/clarifications on twitter; use #BHMPTCP so others can follow along. Winner snags a $100 Amazon gift card!

Hints #0:

  • The latest version of Wireshark supports decoding mptcp options (see “tcp.options.mptcp”).
  • The scapy version in the git repo is based on Nicolas Maitre’s and supports decoding mptcp options. It will help although you don’t strictly need it.
  • The is an mptcp option field to tell the receiver how a tcp packet fits into the overall logical mptcp data flow (what it is and how it works is an exercise for the user 🙂 )
  • It’s possible to get close with techniques that don’t fully understand MPTCP (you’ll know you’re close). However the full solution should match exactly (we’ll use md5sum)

Depending on how people do and questions we get, we’ll update here with a few more hints tonight or tomorrow. Once we’ve got a winner, we’ll post the solution and code examples.

Update: Winners and Solution

We have some winners! Late last night @cozinuzo contacted us with a correct answer, and early this morning @darkfiberiru got it too.

The challenge was created using our fragmenter PoC tool, pushing to a netcat opened socket on an MPTCP-aware destination host:

python -n 9 --file=MPTCP.jpg --first_src_port 46548 -p 3000

The key to this exercise was to look at the mechanism that MPTCP uses to tell how a particular packet fits into the overall data flow. You can see that field in Wireshark as tcp.options.mptcp.dataseqno, or in mptcp-capable scapy as packet[TCPOption_MP].mptcp.dsn.


The mptcp-capable scapy in our mptcp-abuse git repo can easily do the reassembly across all the streams using this field.

Here’s the code (or as a Gist):

# Uses Nicolas Maitre's MPTCP-capable scapy impl, so that should be
# on the python path, or run this from a directory containing that "scapy" dir
from scapy.all import *

packets = rdpcap("pcaps/neohapsis_mptcp_challenge.pcap")
payload_packets = [p for p in packets if TCP in p
                   and p[IP].src in ("", "")
                   and TCPOption_MP in p
                   and p[TCPOption_MP].mptcp.subtype == 2
                   and Raw in p]

f = open("out.jpg", "w")
for p in sorted(payload_packets, key=lambda p: p[TCPOption_MP].mptcp.dsn):

These reassemble to create this image:


The md5sum for the image is 4aacab314ee1a7dc5d73a030067ae0f0, so you’ll know you’ve correctly put the stream back together if your file matches that.

Thanks to everyone who took a crack at it, discussed, and asked questions!

Rob Beck’s MS-SQL Rootkit Framework Presentation @ DefCon Skytalks 2014

SQL Gestalt: A MS-SQL Rootkit Framework will be presented by Rob “whitey” Beck (@damnit_whitey) at the DefCon Skytalks 2014 in Las Vegas, NV this year.  This talk will provide an overview of a basic framework for the creation, deployment, operation, and persistence of a MS-SQL rootkit for all versions of Microsoft SQL Server 2005 and above.


This talk illustrates the various facilities in the MS-SQL database environment for performing code execution.  Using these facilities, attendees are presented with the basis of the SQL Gestalt – A rootkit framework, utilizing various aspects of the SQL core facilities, working in conjunction to provide persistence in the database.


This talk benefits pen testers, forensic analysts, and database administrators by exposing methods and tactics that may not be commonly known or widely employed in traditional database compromises. Examples will be provided in a variety of languages including T-SQL, C#, C++, VBscript, and Powershell utilizing SQL facilities such as SQL Assemblies, the Extended Stored Procedure API, SQL Agent, and OLE Automation.  At the conclusion of this presentation a basic framework will be released with sample code to illustrate all of the functionality discussed in this talk.

Talk Agenda

The following topics will be discussed in the presentation:

  • Concept of the SQL Gestalt rootkit
  • Facilities for executable code in SQL
    • Overview
    • Advantages
    • Disadvantages
    • Examples
  • Module installation
    • Deployment
    • Execution considerations
  • Securing a native code execution point
  • Persistence in SQL
  • Advanced rootkit operations


Multipath TCP – BlackHat Briefings Teaser

Multipath TCP: Breaking Today’s networks with Tomorrow’s Protocols. is being presented at Blackhat USA this year by Me (Catherine Pearce @secvalve) as well as Patrick Thomas @coffeetocode. Here is a bit of a tease, it’s a couple of weeks out yet, but we’re really looking forward to it.

Come see us at Black Hat Briefings in South Seas AB, on Wednesday at 3:30pm.

(UPDATE 8/14: A followup post and the talk slides are now online.)

What is multipath TCP?

Multipath TCP is a backwards-compatible modification that allows a core networking protocol, TCP to talk over multiple paths at the same time. In short, Multipath TCP decouples TCP from a specific IP address, and it also allows you to add and remove network addresses on the fly.

Multipath TCP in brief

Multipath TCP splits connection data across N different TCP subflows



Why do I care?

MPTCP Changes things for security in a few key ways:

  • Breaks Traffic Inspection – If you’re inspecting traffic you need to be able to correlate and reassemble it. We haven’t found a single security technology which does so currently.
  • Changes network Trust models – Multipath TCP allows you to spread traffic around, and also remove the inherent trust you place in any single network provider. With MPTCP it becomes much harder for a single network provider to undetectably alter or sniff your traffic unless they collaborate with the other ones you are using for that connection.
  • Creates ambiguity about incoming and outgoing connections – The protocol allows a client to tell a server that it has another address which the server may connect back to. To a firewall that doesn’t understand MPTCP it looks like an outgoing connection.
MPTCP and Reverse connections

MPTCP can have outbound incoming connections!?



Backwards compatible

Did I mention that MPTCP is designed to be backwards compatible and runs on >= 85% of existing network infrastructure [How Hard Can It Be? Designing and Implementing a Deployable Multipath TCP ]

Like IPv6, this is a technology that will slowly appear in network devices and can cause serious security side effects if not understood and properly managed. MPTCP affects far more than addressing though, it also fundamentally changes how TCP traffic flows over networks.

MPTCP confuses your existing approaches and tools

If you don’t understand MPTCP, things get really confusing. Take this wireshark “follow TCP stream” where I follow an http connection. Why does the server reply to an invalid request this way?

MPTCP Fragmentation confuses wireshark

Why does the web server reply to this garbled message? – MPTCP Confuses even tools that support it


Network flows can also become a lot more complicated. Why talk over a single network path when you can talk through all possible paths?


That’s what your non MPTCP-aware flows look like.

But, if we are able to understand it then it makes a lot more sense:


What are the implications?

Technologies are changing, and multipath technologies look like a sure thing in a decade or two. But, security isn’t keeping up with the new challenges, let alone the new technologies.

  1. I can use MPTCP to break your IDS, DLP, and many application-layer security devices today.
  2. There are security implications in multipath communications that we cannot patch our existing tools to cope with, we need to change how we do things. Right now tools can correlate flows from different points on the network, but they are incapable of handling data when part of it flows down one path and part of it flows down another.

To illustrate point 2:

What if you saw this across two subflows… Can you work out what they should be?

  • Thquicown fox jps ov the az og
  • E k brumerlyd.

Highlight the text below to see what that reassembles to

[The quick brown fox jumps over the lazy dog.]

Follow up with our Black Hat session as we discuss MPTCP and the effect on security in yet more detail. We ma not be ready for the future, but it is fast approach, just ask Siri.

How does your security decide what to do with a random fragment of a communication?



Cached Domain Credentials in Vista/7 (aka why full drive encryption is important)

Recently, I was conducting a security policy audit of a mid-size tech company and asked if they were using any form of disk encryption on their employee’s workstations. They were not, however they pointed me to a policy document that required all “sensitive” files to be stored in an encrypted folder on the User’s desktop. They assumed that this was adequate protection against the files being recovered should the laptop be lost or stolen.

Unfortunately, this is not the case. Without full disk encryption (like BitLocker), sensitive system files will always be available to an attacker, and credentials can be compromised. Since Windows file encryption is based on user credentials (either local or AD), once these creds are compromised, an attacker would have full access to all “encrypted” files on the system. I will outline an attack scenario below to stress the importance of full drive encryption.



If you are not familiar, Windows has a built in file encryption function called Encrypting File System (EFS) that has been around since Windows 2000. If you right click on a file or folder and go to Properties->Advanced you can check a box called “Encrypt contents to secure data”. When this box is checked, Windows will encrypt the folder and its contents using EFS, and the folder or file will appear green in Explorer to indicate that it is protected:

Encrypted Directory


Now only that user will be able to open the file. Even Administrators will be denied from viewing it. Here a Domain Admin (‘God’) is attempting to open the encrypted file that was created by a normal user (‘nharpsis’):




According to Microsoft’s TechNet article on EFS, “When files are encrypted, their data is protected even if an attacker has full access to the computer’s data storage.” Unfortunately, this is not quite true. The encrypted file above (“secret.txt”) will be decrypted automatically and viewable whenever ‘nharpsis’ logs in to the machine. Therefore to view the files, an attacker only needs to compromise the ‘nharpsis’ account.



In this attack scenario, we will assume that a laptop has been lost or stolen and is powered off. There are plenty of ways to mount an online attack against Windows or extract credentials and secret keys straight from memory. Tools like mimikatz or the Volatility Framework excel at these attacks.

For a purely offline attack, we will boot from a live Kali Linux image and mount the Windows hard drive. As you can see, even though we have mounted the Windows partition and have read/write access to it, we are unable to view files encrypted with EFS:

Permission Denied - Kali

Yes you read that right. We are root and we are seeing a “Permission denied”.

Commercial forensic tools like EnCase have functionality to decrypt EFS, but even they require the username and password of the user who encrypted it. So the first step will be to recover Ned Harpsis’s credentials.


Dumping Credentials

There are numerous ways to recover or bypass local accounts on a windows machine. SAMDUMP2 and ‘chntpw’ are included with Kali Linux and do a nice job of dumping NTLM hashes and resetting account passwords, respectively. However, in this instance, and the instance of the company I was auditing, these machines are part of a domain and AD credentials are used to log in.

Windows caches domain credentials locally to facilitate logging in when the Domain Controller is unreachable. This is how you can log in to your company laptop when traveling or on a different network. If any domain user, including admins, have logged in to this machine, his/her username and a hash of his password will be stored in one of the registry hives.

Kali Linux includes the tool ‘cachedump’ which is intended to be used just for this purpose. Cachedump is part of a larger suite of awesome Python tools called ‘creddump’ that is available in a public svn repo:

Unfortunately, creddump has not been updated in several years, and you will quickly realize when you try to run it that it does not work on Windows 7:

Cachedump Fail

This is a known issue and is discussed on the official Google Code project.

As a user pointed out, the issue persisted over to the Volatility project and an issue was raised there as well. A helpful user released a patch file for the cachedump program to work with Windows 7 and Vista.

After applying the patches and fixes I found online, as well as some minor adjustments for my own sanity, I got creddump working on my local Kali machine.

For convenience’s sake, I have forked the original Google Code project and applied the patches and adjustments. You can find the updated and working version of creddump on the Neohapsis Github:


Now that I had a working version of the program, it was just a matter of getting it on to my booted Kali instance and running it against the mounted Windows partition:

Creddump in action

Bingo! We have recovered two hashed passwords: one for ‘nharpsis’, the user who encrypted the initial file, and ‘god’, a Domain Admin who had previously logged in to the system.


Cracking the Hashes

Unlike locally stored credentials, these are not NT hashes. Instead, they are in a format known as ‘Domain Cache Credentials 2’ or ‘mscash2’, which uses PBKDF2 to derive the hashes. Unfortunately, PBKDF2 is a computation heavy function, which significantly slows down the cracking process.

Both John and oclHashcat support the ‘mscash2’ format. When using John, I recommend just sticking to a relatively short wordlist and not to pure bruteforce it.

If you want to attempt to use a large wordlist with some transformative rules or run pure bruteforce, use a GPU cracker with oclHashcat and still be prepared to wait a while.

To prove that cracking works, I used a wordlist I knew contained the plaintext passwords. Here’s John cracking the domain hashes:

Cracked with John

Note the format is “mscash2”. The Domain Admin’s password is “g0d”, and nharpsis’s password is “Welcome1!”

I also extracted the hashes and ran them on our powerful GPU cracking box here at Neohapsis. For oclHashcat, each line must be in the format ‘hash:username’, and the code for mscash2 is ‘-m 2100’:




Accessing the encrypted files

Now that we have the password for the user ‘nharpsis’, the simplest way to retrieve the encrypted file is just to boot the laptop back into Windows and log in as ‘nharpsis’. Once you are logged in, Windows kindly decrypts the files for you, and we can just open them up:




As you can see, if an attacker has physical access to the hard drive, EFS is only as strong as the users login password. Given this is a purely offline attack, an attacker has unlimited time to crack the password and then access the sensitive information.

So what can you do? Enforce full drive encryption. When BitLocker is enabled, everything in the drive is encrypted, including the location of the cached credentials. Yes, there are attacks agains BitLocker encryption, but they are much more difficult then attacking a user’s password.

In the end, I outlined the above attack scenario to my client and recommended they amend their policy to include mandatory full drive encryption. Hopefully this straightforward scenario shows that solely relying on EFS to protect sensitive files from unauthorized access in the event of a lost or stolen device is an inadequate control.




Smart TV + Smartphone = Shiny New Attack Surfaces

According to a Gartner report from December 2012, “85 percent of all flat-panel TVs will be Internet-connected Smart TVs by 2016.” Forbes magazine gives some analysis about what is fueling this trend: , The article makes a mention of “DIAL”, an enabling technology for second-screen features (which this post is about).  With these new devices come new risks as evidenced in the following article: , as well as more recent research about Smart TV risks presented at the CanSecWest and DefCon security conference this year (2013).

For more details about about exactly what features a Smart TV has above and beyond a normal television, consult this WikiPedia article:

This post introduces and describes aspects of “DIAL”, a protocol developed by Google and Netflix for controlling Smart TVs with smart phones and tablets.  DIAL provides “second screen” features, which allow users to watch videos and other content on a TV using a smart phone or tablet. This article will review sample code for network discovery and enumerate Smart TV apps using this protocol.

Part 1: Discovery and Enumeration

Smart TVs are similar to other modern devices in that they have apps. Smart TVs normally ship with an app for YouTube(tm), Netflix(tm), as well as many other built-in apps. If you have a smartphone, then maybe you’ve noticed that when your smartphone and TV are on the same network, a small square icon appears in some mobile apps, allowing you to play videos on the big TV. This allows you to control the TV apps from your smartphone. Using this setup, the TV is a “first screen” device, and the phone or tablet functions as a “second screen”, controlling the first screen.

DIAL is the network protocol used for these features and is a standard developed jointly between Google and Netflix.  (See ).  DIAL stands for “Discovery and Launch”. This sounds vaguely similar to other network protocols, namely “RPC” (remote procedure call). Basically, DIAL gives devices a way to quickly locate specified networked devices (TVs) and controlling programs (apps) on those devices.

Let’s take a look at the YouTube mobile application to see how exactly this magic happens. Launching the YouTube mobile app with a Smart TV on network (turned on of course) shows the magic square indicating a DIAL-enabled screen is available:

Magic TV Square

Square appears when YouTube app finds TVs on the network.

Clicking the square provides a selection menu where the user may choose which screen to play YouTube videos. Recent versions of the YouTube apps allow “one touch pairing” which makes all of the setup easy for the user:


Let’s examine the traffic generated by the YouTube mobile app at launch.

  • The Youtube mobile app send an initial SSDP request, to discover available first-screen devices on the network.
  • The sent packet is destined for a multicast address ( on UDP port 1900. Multicast is useful because devices on the local subnet can listen for it, even though it is not specifically sent to them.
  • The YouTube app multicast packet contains the string “urn:dial-multiscreen-org:service:dial:1”. A Smart TV will respond to this request, telling YouTube mobile app its network address and information about how to access it.

A broadcast search request from the YouTube mobile app looks like this:

11:22:33.361831 IP my_phone.41742 > UDP, length 125
0x0010: .......l..+;M-SE
0x0020: ARCH.*.HTTP/1.1.
0x0030: .HOST:.239.255.2
0x0040: 55.250:1900..MAN
0x0050: :."ssdp:discover
0x0060: "..MX:.1..ST:.ur
0x0070: n:dial-multiscre
0x0080: en-org:service:d
0x0090: ial:1....

Of course, the YouTube app isn’t the only program that can discover ready-to-use Smart TVs. The following is a DIAL discoverer in a few lines of python. It waits 5 seconds for responses from listening TVs. (Note: the request sent in this script is minimal. The DIAL protocol specification has a full request packet example.)

! /usr/bin/env python
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.sendto("ST: urn:dial-multiscreen-org:service:dial:1",("",1900))
while 1:
    data,addr = s.recvfrom(1024)
    print "[*] response from %s:%d" % addr
    print data
  except socket.timeout:

A response from a listening Smart TV on the network looks like:

[*] response from
HTTP/1.1 200 OK
CACHE-CONTROL: max-age=1800
SERVER: Linux/2.6 UPnP/1.0 quick_ssdp/1.0
ST: urn:dial-multiscreen-org:service:dial:1
USN: uuid:bcb36992-2281-12e4-8000-006b9e40ad7d::urn:dial-multiscreen-org:service:dial:1

Notice that the TV returns a LOCATION header, with a URL: . The response from reading that URL leads to yet another URL which provides the “apps” link on the TV.

HTTP/1.1 200 OK
Content-Type: application/xml
<?xml version="1.0"?><root xmlns="urn:schemas-upnp-org:device-1-0" xmlns:r="urn:restful-tv-org:schemas:upnp-dd”> <specVersion> <major>1</major> <minor>0</minor> </specVersion>
<device> <deviceType>urn:schemas-upnp-org:device:tvdevice:1</deviceType> <friendlyName>Vizio DTV</friendlyName> <manufacturer>Vizio Inc.</manufacturer> <modelName>Vizio_E420i_A0</modelName>
<UDN>uuid:bcb36992-2281-12e4-8000-006b9e40ad7d M-SEARCH * HTTP/1.1
MAN: "ssdp:discover"
MX: 3
ST: urn:schemas-upnp-org:device:MediaServer:1

At this point, the YouTube mobile app will try to access the “apps” URL combined with the application name with a GET request to: http::// . A positive response indicates the application is available, and returns an XML document detailing some data about the application state and feature support:

HTTP/1.1 200 OK
Content-Type: application/xml

<?xml version="1.0" encoding="UTF-8"?>
<service xmlns="urn:dial-multiscreen-org:schemas:dial">
<options allowStop="false"/>

Those of you who have been following along may have noticed how easy this has been. So far, we have sent one UDP packet and issued two GET requests. This has netted us:

  • The IP address of a Smart TV
  • The Operating system of a Smart TV (Linux 2.6)
  • Two listening web services on random high ports.
  • A RESTful control interface to the TV’s YouTube application.

If only all networked applications/attack surfaces could be discovered this easily. What should we do next? Let’s make a scanner. After getting the current list of all registered application names (as of Sept 18, 2013)  from the DIAL website, it is straightforward to create a quick and dirty scanner to find the apps on a Smart TV:

#! /usr/bin/env python
# Enumerate apps on a SmartTV
# <>
import urllib2
import sys
'Twonky TV','Turner-TNT-Leverage','Turner-TBS-BBT','Turner-NBA-GameTime',
'org.enlearn.Copilot','frequency', 'PlayMovies' ]
  url = sys.argv[1]
  print "Usage: %s tv_apps_url" % sys.argv[0]

for app in apps:
    u = urllib2.urlopen("%s/%s"%(url,app))
    print "%s:%s" % ( app, repr(str(u.headers) )

Some of those app names appear pretty interesting. (Note to self: Find all corresponding apps.) The scanner looks for URLs returning positive responses (200 result codes and some XML), and prints them out:

 $ ./ 

YouTube:'Content-Type: application/xml\r\n<?xml version="1.0" encoding="UTF-8"?>\r\n<service xmlns="urn:dial-multiscreen-org:schemas:dial">\r\n  <name>YouTube</name>\r\n  <options allowStop="false"/>\r\n  <state>stopped</state>\r\n</service>\r\n'

Netflix:'Content-Type: application/xml\r\n<?xml version="1.0" encoding="UTF-8"?>\r\n<service xmlns="urn:dial-multiscreen-org:schemas:dial">\r\n  <name>Netflix</name>\r\n  <options allowStop="false"/>\r\n  <state>stopped</state>\r\n</service>\r\n'

Hopefully this article has been informative for those who may be looking for new devices and attack surfaces to investigate during application or penetration testing.


Signatures or PINs? EMV is Coming

Whether you are a seasoned, international road warrior, or a domestic suburbanite, new security features will soon be showing up on a credit card near you. In light of recent card data compromises, there’s a new drive to adopt credit card security technologies known as “Chip and PIN” (typically noted as “chip/PIN”) to better secure credit card data against fraud or compromise. While chip/PIN is new to most U.S. cardholders, it is the norm across most of Europe, Canada, and Mexico. There have been many initiatives in the last several years to drive U.S. payment card systems towards more secure technologies, but only now is adoption of chip/PIN starting to get increased traction across the U.S. payment card industry.

For individual card holders, these developments are important, and in this post we will cover some of the key points of these technologies.


First, what exactly is chip/PIN and what does it do to protect credit card data?

In a chip/PIN environment, when purchasing goods at a point of sale (POS) device, the credit card is inserted or “dipped” into a card reading device—not swiped as it is in the U.S. Once inserted, the customer inputs a PIN which authenticates the cardholder against the chip embedded on the card. Upon successful authentication, the chip generates the data necessary to complete the transaction and transmits the data for authorization.

Before we get too far into the discussion about chip/PIN, there is one point that needs to be clarified: The chip component of chip/PIN cards is sometimes referred to as “EMV data” or “EMV transactions” in the payment industry. The term EMV (for Europay, MasterCard and Visa) refers to a standard definition for chip-based payment cards, or “chip cards”—also referred to as “IC (integrated circuit) cards” as defined by EMVCo LLC. EMV is the basis for the chip/PIN implementation throughout Europe, and is planned for implementation in the U.S. (more on that, below). In short, EMV refers to the “chip” portion of chip/PIN cards, with the “PIN” implementation being a separate matter entirely.

Why is this relevant? Because much of what has been discussed thus far about implementing chip cards in the U.S. is focused primarily on the “chip” component, and does not necessarily include the “PIN” component that is otherwise present in Europe’s EMV environment. In lieu of using a PIN to authenticate the chip card, discussions in the U.S. have leaned toward reliance on manual signature verification (such as when a clerk compares the signature on the receipt to the signature on the card). As a result, the U.S. implementation will likely wind up being referred to as “chip and signature” or “chip/signature.”


What’s the difference between chip/PIN and chip/signature?

From the merchant’s perspective the credit-card payment process wouldn’t change significantly, outside of likely hardware upgrade requirements. And from the processor’s perspective, there really isn’t a difference, as long as they process or support transactions using EMV, or “track-equivalent data.”

Track-equivalent data is the data — including cryptographic data — used for transaction authentication and authorization within EMV environments. It is generated by the on-board integrated circuit, or the “chip,” on the card itself—not the card-reading device. This is not to say that track-equivalent data is “secure” in-and-of-itself. Because of some of the underlying functional requirements, track-equivalent data typically includes certain discretionary data elements, some of which are sensitive in nature and cannot be stored (something merchants should note).

From the cardholder perspective, however, there is one notable difference and that is the requirement of a PIN or signature to verify that the person holding the card is the actual card owner.


Is chip/PIN more or less secure than chip/signature?

That depends.

In a chip/PIN scenario, the PIN is used to authenticate the cardholder against the information stored on the chip. If you don’t know the PIN, the chip won’t give up the information necessary to complete the transaction. In a chip/signature scenario (theoretically speaking), the clerk responsible for completing the transaction would be required to validate the customer signature on the receipt with their signature on the card. If your signature doesn’t match sufficiently enough per the clerk’s perusal, they won’t complete the transaction. Say what you will about how consistently the practice of signature verification is actually practiced, versus how it is supposed to in theory, there are equally compelling arguments for either approach.

In a chip/PIN environment, as long as the cardholder’s PIN is kept secret, it would be theoretically impossible for someone to use a stolen card to perform fraudulent card-present transactions. It is because of the PIN requirement that card criminals have evolved their data collection strategies to include video surveillance targeting PIN entry devices, such as at ATMs and retail point-of-sale devices, to collect customer PINs. Once the PIN is compromised, the card can be used for fraudulent transactions. On the other hand, I can show my signature around to anyone, put it on all my receipts, etc., and the likelihood of anyone being able to reliably reproduce it on demand is pretty slim (expert forgers, excluded). Ultimately, the question boils down to this: Which is a more secure means to verify that a credit card belongs to the person holding the card?



It can be erroneously concluded that U.S. implementation of EMV heading in the direction of chip/signature undermines many of the anti-fraud security protections of chip/PIN. However, when the issue is considered from multiple sides, especially in putting everything together for this article, the more it is clear that there is no significant security benefit of one solution over the other.  Whether it is PIN or signature, the control is only used to authenticate the cardholder—the rest is about implementing security controls via EMV and integrated circuit cards that has nothing to do with either PINs or signatures. Until there is historical data to demonstrate the effectiveness or ineffectiveness of signatures vs. PINs in reducing card fraud, the jury is still out on which solution offers a significant upside over alternatives.

Ultimately, whether cards are authenticated via PIN or signature, the chip-based credit cards being rolled out in the U.S. will rely upon EMV security measures to protect the security of credit card data. These technologies provide a solid foundation for improving the overall security of credit card information and limiting fraud and misuse of compromised credit card data.



EMVCo LLC Website:

Wikipedia: EMV