CS162Operating Systems andSystems ProgrammingLecture 27Peer-to-peer Systemsand Other TopicsDecember 7th, 2005Prof. John Kubiatowiczhttp://inst.eecs.berkeley.edu/~cs162Lec 27.212/07/05Kubiatowicz CS162 ©UCB Fall 2005Goals for Today• A couple of requested topics– Windows vs. Linux– Trusted Computing• Peer-to-Peer Systems– OceanStoreNote: Some slides and/or pictures in the following areadapted from slides ©2005 Silberschatz, Galvin, and Gagne Lec 27.312/07/05Kubiatowicz CS162 ©UCB Fall 2005Requests for Final topics• Some topics people requested:– More about device drivers– Xbox/Playstation/gamecube/etc operating systems– Windows vs Linux– Trusted computing platforms• About Device Drivers– Well, very complex topic. – Documentation associated with various operating systems» Many similarities, many differences– Good place to start: » Chapter 6 of “The design and Implementation of the 4.4 BSD Operating System” (on reserve for this class)• Xbox vs Playstation etc– Well, most of these are custom OSs.» Original Xbox ran modified version of Window 2000» New Xbox 360 rumored to run modified version of original Xbox OS (i.e. a modified2version of Windows 2000)– Most important property: Real Time scheduling» Ability to meet scheduling deadlinesLec 27.412/07/05Kubiatowicz CS162 ©UCB Fall 2005Windows vs Linux• Windows came from personal computer domain– Add-on to IBM PC providing a windowing user interface» Became “good at” doing graphical interfaces– Didn’t have protection until Windows NT» Multiple users supported (starting with Window NT), but can’t necessarily have multiple GUIs running at same time– Product differentiation model:» Purchase separate products to get email, web servers, file servers, compilers, debuggers…• Linux came from long line of UNIX Mainframe OSs– Targeted at high-performance computation and I/O» High performance servers» GUI historically lacking compared to Windows– Protection model from beginning» Multiple users supported at core of OS– Full function Mainframe OS: email, web servers, file servers, ftp servers, compilers, debuggers, etc.Lec 27.512/07/05Kubiatowicz CS162 ©UCB Fall 2005• Internal Structure is different– Windows XP evolved from NT which was a microkernel» Core “executive” runs in protected mode» Many services run in user mode (Although Windowing runs inside kernel for performance)» Object-oriented design: communication by passing objects» Event registration model: many subsystems can ask for callbacks when events happen» Loadable modules for device drivers and system extension– Linux Evolved from monolithic kernel» Many portions of kernel operate in same address space» Loadable modules for device drivers and system extension» Fewer layers ⇒ higher performance• Source Code development model– Windows: closed code development» Must sign non-disclosure to get access to source code» “Cathedral” model of development: only Microsoft’s developers produce code for Windows– Linux: open development model» All distributions make source code available to analyze» “Bazaar” model of development: many on the net contribute to making Linux distribution Windows vs LinuxLec 27.612/07/05Kubiatowicz CS162 ©UCB Fall 2005• Perceptions:– Windows has more bugs/is more vulnerable to viruses?» True? Hard to say for sure» More Windows systems ⇒ more interesting for hackers– Linux simpler to manage?» True? Well, Windows has hidden info (e.g. registry)» Linux has all configuration available in clear text– Microsoft is untrustworthy? Many distrust “the man”» Quick to adopt things like Digital Rights Management (DRM)» Quick to embrace new models of income such as software rental which counter traditional understanding of software– Windows is slow?» This definitely seemed to be true with earlier versions» Less true now, but complexity may still get in way• Why choose one over other?– Which has greater diversity of graphical programs?» Probably Windows– Which cheaper? Well, versions of Linux are “free– Which better for developing code and managing servers?» Probably Linux, although this is changing» OS API (e.g. system calls) definitely seem simplerWindows vs LinuxLec 27.712/07/05Kubiatowicz CS162 ©UCB Fall 2005Trusted Computing• Problem: Can’t trust that software is correct– Viruses/Worms install themselves into kernel or system without users knowledge– Rootkit: software tools to conceal running processes, files or system data, which helps an intruder maintain access to a system without the user's knowledge– How do you know that software won’t leak private information or further compromise user’s access?• A solution: What if there were a secure way to validate all software running on system?– Idea: Compute a cryptographic hash of BIOS, Kernel, crucial programs, etc.– Then, if hashes don’t match, know have problem• Further extension:– Secure attestation: ability to prove to a remote party that local machine is running correct software– Reason: allow remote user to avoid interacting with compromised system• Challenge: How to do this in an unhackable way– Must have hardware components somewhereLec 27.812/07/05Kubiatowicz CS162 ©UCB Fall 2005TCPA: Trusted Computing Platform Alliance• Idea: Add a Trusted Platform Module (TPM)• Founded in 1999: Compaq, HP, IBM, Intel, Microsoft• Currently more than 200 members• Changes to platform– Extra: Trusted Platform Module (TPM)– Software changes: BIOS + OS• Main properties– Secure bootstrap– Platform attestation– Protected storage• Microsoft version:– Palladium– Note quite same: More extensive hardware/software systemATMEL TPM Chip(Used in IBM equipment)Lec 27.912/07/05Kubiatowicz CS162 ©UCB Fall 2005Trusted Platform Module• Cryptographic operations– Hashing: SHA-1, HMAC– Random number generator– Asymmetric key generation: RSA (512, 1024, 2048)– Asymmetric encryption/ decryption: RSA–Symmetric encryption/ decryption: DES, 3DES (AES)• Tamper resistant (hash and key) storageVolatileMemoryNon-volatileMemoryFunctionalUnitsRSA Key Slot-0…RSA Key Slot-9PCR-0…PCR-15Auth SessionHandlesKey HandlesOwner Auth Secret(160 Bits)Storage Root Key(2048 Bits)Endorsement Key(2048 Bits)RSA Encrypt/DecryptSHA-1HashRandom NumGeneratorHMACRSA KeyGenerationLec 27.1012/07/05Kubiatowicz CS162 ©UCB Fall 2005TCPA: PCR Reporting Value •
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