Understanding Security APIs - CrySyS Lab

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it spawned the development of control equipment to make it difficult for soldiers working with nuclear ordinance to deploy weapons without proper authorisation. At the time, the major perceived threat to nuclear ordinance was that of regime change in allied countries entrusted with the weapons. These controls centred around Permissive Action Links (PALs): electronics in the ordinance which enforced access control to the mechanical core of the device. The conjunction of cryptographic functionality with the security policies inherent in tamper-resistance and access control gave rise to Security APIs as we know them today. However, it took the ‘killer app’ of ATM security to introduce Security APIs to the commercial world. 2.2 The ‘Killer App’ The ATMs which are now a common feature of everyday life have taken several decades to develop. They started out as cash-dispensing devices purely for increased speed of service, and are now quite independent multi-purpose devices that provide banking services in hostile environments. As the international ATM network grew, the concentration points of the networks – the bank mainframes – held more and more valuable secrets, and enforcement of policy on usage of their APIs became crucial. Some of the early adopters had the security relevant code integrated with application code inside their mainframes. Thus, the highly sensitive keys used to determine customer PINs were stored in the RAM of the mainframe, and there would be a number of employees with sufficient access to see them, if motivated. This risk was then mitigated by identifying and isolating the security-relevant code from the rest of the banking applications, yet within the same mainframe. Some of the first Security APIs were created here – between software modules written by different programmers. However, as the overall complexity of operating systems rose, it became clear that the keys were at risk from the maintenance staff, who needed full access to all parts of a mainframe to maintain and upgrade the software. Furthermore, it seemed unwise to put keys that were vital to the economic security of the bank at risk from bugs in third-party code (not designed with security considerations) that could compromise the security relevant code. It could also be argued that all mainframe operating systems were so complex as to make bug-free implementation unattainable, regardless of whether they had been designed with security in mind. The concept of a “Hardware Security Module” (HSM) or “Cryptoprocessor” arose in part to address this problem. These implemented the existing Security APIs, but with physical separation of the computing platforms, enabling separate administration of the devices. To be successful, these modules had to fulfil two aims: 18
• To isolate and define the code which was security relevant, and to physically separate it into a device not under control of the system administrators. • To minimise the amount of security relevant code, and to keep the rules governing its use as simple as possible, so that it would be easier to avoid bugs. In practical terms, financial HSMs were entrusted with the secret keys used for deriving customer PINs from account numbers. Their policy was to ensure that all PINs stayed in encrypted form, and clear PINs would never be available to host programmers (they could only be sent in the clear to a secure printer locked in a cage). As HSMs began to move away from mainframes into high end servers, and onto the desks of operators, physical tamper-resistance was added to the logical Security API. These financial APIs are still in existence today, are used by banks all over the world, and have not been substantially redesigned since their first inception. 2.3 The Present The next significant advance was when Security APIs were used to enforce more complex policies than just protecting secrecy of keys. The introduction of electronic credit tokens for prepayment services such as electricity meters (and most recently mobile phones) gave rise to a new application – credit dispensing. A Security API could have a policy allowing the repeated execution of a credit dispensing command, deducting an amount from a credit counter each time. The mid-nineties has seen new applications for Security APIs: securing certification authorities and internet payment infrastructures. In addition, embedded devices such as smartcards, which are much smaller and more numerous than hardware security modules (HSMs), are beginning to add policy enforcement to their APIs. So security and cryptography are no longer restricted to the military and banking worlds. Now that corporations and individuals have seized the initiative, wherever competition arises in life, the tools of the security world can go to work protecting people’s interests. Security considerations are about to become ubiquitous: every major operating system ships with substantial crypto facilities, and so do mobile phones. With the rise of wireless communications, we will see “home area networks” becoming established, and even washing machines and fridges will use embedded cryptographic controllers to communicate securely over the airwaves. –And with every application that uses security comes a ‘Security API’, forming the interface between the application code and the security relevant code. 19
Page 1 and 2: Understanding Security APIs Michael
Page 3: Dedication To Philip Barnes, who co
Page 6 and 7: Understanding Security APIs Michael
Page 8 and 9: 4.3 Certification Authorities . . .
Page 10 and 11: 7.3.1 VSM Compatibles - XOR to Null
Page 12 and 13: Chapter 1 Introduction In today’s
Page 14 and 15: Whatever you intend to get out of t
Page 16 and 17: The aspects of the research relatin
Page 20 and 21: 2.4 Key Dates Year Events 1960 Deve
Page 22 and 23: ciphertext into a four digit number
Page 24 and 25: service engineer). In order for the
Page 26 and 27: 3.3 Development of the Attack Toolk
Page 28 and 29: This key binding attack effectively
Page 30 and 31: Chapter 4 Applications of Security
Page 32 and 33: Higher-level goals maybe to achieve
Page 34 and 35: VISA. It also permits end-to-end co
Page 36 and 37: There are three sorts of threat to
Page 38 and 39: control - and would typically be is
Page 40 and 41: Secure Computing Base (NGSCB), prev
Page 42 and 43: Chapter 5 The Security API Industry
Page 44 and 45: • Individuals, Customers, Clients
Page 46 and 47: 5.2.2 1990 to 2000 Year Events 1991
Page 48 and 49: 5.3 Summary of HSM Manufacturers 5.
Page 50 and 51: pose crypto platform market, and si
Page 52 and 53: 5.3.8 Baltimore http://www.baltimor
Page 54 and 55: The Trusted Computing Group will li
Page 56 and 57: available, but should be carefully
Page 58 and 59: Chapter 6 Hardware Security Modules
Page 60 and 61: an increasing concern as the device
Page 62 and 63: • Potting is nowadays one of the
Page 64 and 65: • Light Sensors can be coupled wi
Page 66 and 67: 6.2.1 Tamper-Evidence Hardware Secu
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6.3 HSM Summary This section introd
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6.3.3 nCipher nForce API nCore API
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6.3.5 nCipher netHSM API nCore API
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6.3.7 Thales RG7000 API Proprietary
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6.3.9 Chrysalis-ITS Luna CA3 API PK
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Chapter 7 Analysis of Security APIs
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First Command: Key Part Import User
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achieve the same functionality as o
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Figure 7.5 shows a common key manag
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7.2 The Attacker’s Toolkit This s
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early HSMs actually used this techn
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PIN numbers are often stored in enc
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operating systems. Naively implemen
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The supervisor key switch is turned
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7.3.4 4758 CCA - Key Import Attack
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7.3.6 4758 CCA - 3DES Key Binding A
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Bank Home Bank Home Bank Home Test
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the number of operations the HSM wo
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Implementation Overview The DES cra
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7.3.8 4758 CCA - Weak Key Timing At
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which is a many-to-one mapping betw
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Digits Possibilities A AAAA(1) AB A
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No # Poss. pins Decimalisation tabl
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tables in a generic way will be har
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Security Officer 1 -> HSM : SM?IK 8
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in. Consider the example below, whi
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Indeed it now seems that many conve
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• Search Tools - such as PROLOG -
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\% these are the commands provided
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--------------------------SPASS-STA
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Problem Specification The API is sp
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UI Decisions Figure 7.23: The MIMse
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Figure 7.25: The MIMsearch ‘Watch
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2. If the Security API prevents cer
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it can be enabled and disabled, the
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• When the host machine sends dat
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8.2.5 Legacy Issues • Isolate you
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The Visa Security Module had a seri
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Class I Passive tokens, which prese
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Smartcards Figure 8.2: Chrysalis Lu
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link to the authorisation process f
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To minimise the risk of breach, eac
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When no privileged operations are r
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8.4.3 How Many Security Officers ar
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Chapter 9 The Future of Security AP
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e unable to assure themselves that
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9.4 The Bottom Line Whilst it is ex
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10.1 Roles and Responsibilities Sec
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Chapter 11 Glossary 4753 IBM Crypto
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PKCS#11 Public Key Cryptography Sta
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[14] J. Clulow, “On the Security
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[53] http://www.cl.cam.ac.uk/~rnc1/
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