Spring 2006 CS 155 Digital Rights Management John

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Spring 2006 CS 155 Digital Rights Management John Mitchell

Spring 2006 CS 155 Digital Rights Management John Mitchell

Next Tuesday Aaron Sigel Apple Security Team 2

Next Tuesday Aaron Sigel Apple Security Team 2

Basic Problem Joey writes and records a song n n n Song distributed on

Basic Problem Joey writes and records a song n n n Song distributed on some sort of media Joey (and music company) want to sell recordings But digital info is easy to copy, on most media What can Joey (and Music Inc. ) try to do? n n n 3 Look for copies? Mark recording to make it easier to find copies? Restrict media so only certain devices can play it? All of these approaches have problems; no perfect solution (yet? )

Outline Legal landscape n Copyright law, fair use, DMCA Examine or modify content n

Outline Legal landscape n Copyright law, fair use, DMCA Examine or modify content n n n Content hashing and copyright crawling Watermarking Fingerprinting Regulate use through special content players n n Apply complex policies, need tamper-proof platform Some examples w w 4 Media. Max CD 3: restrict access on software players DVDs: CSS encryption and hardware/software players Windows Media Rights Management Office Information Rights Management

Basis for U. S. Copyright Law U. S. Constitution (A 1, S 8, C

Basis for U. S. Copyright Law U. S. Constitution (A 1, S 8, C 8): n "Congress shall have power. . . to promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries” Intro of printing press in England in 1400 s n n control (censor) publication of books maintain registry of legal books 1710 law to protect authors’ works n 5 prevent another person from re-producing a book and putting their name on it

U. S. Copyright Law Balance two competing objectives n n Protect works so the

U. S. Copyright Law Balance two competing objectives n n Protect works so the author gets financial reward Promote access: progress of science, arts Gives exclusive rights for limited time n n Reproduce the work, derive new works, distribute copies, perform or display it publicly Extends to life of author plus 70 years Applies to n n 6 “original works of authorship” fixed in tangible medium of expression literary, dramatic, artistic, musical, pictorial, architectural works – software? hyperlinks?

Fair Use Legal use of copyrighted works for education, research, reporting, etc. n must

Fair Use Legal use of copyrighted works for education, research, reporting, etc. n must provide transformative value Determined by four factors n n 7 purpose and character of the use nature of the copyrighted work amount of the copyrighted work used effect on market value of copyrighted work

Enforcement of copyright law Anyone here get a letter? n n Music industry monitors

Enforcement of copyright law Anyone here get a letter? n n Music industry monitors file sharing Law specifies high minimum penalties w Recipients usually offered a chance to settle for ~$3000 n See: http: //www. eff. org/wp/how-not-get-sued-file-sharing Limitations of copyright law n Coarse-grained protection, hard to enforce Next topic n 8 Technology used to help enforce copyright

Content hashing Suppose we had a “content-aware” hash function: H: {music} {short strings} satisfying:

Content hashing Suppose we had a “content-aware” hash function: H: {music} {short strings} satisfying: n n 1. If M 1 and M 2 are two music clips (e. g. MP 3 files) that play the “same” song then H(M 1) = H(M 2) 2. Given a clip M a pirate cannot create an “acceptable” clip M’ such that H(M) H(M’) Is this realistic? n n Hash function must resist all signal processing tricks Do not know such hash functions exist w some claim to have them 9

Copyright Crawler Web crawler looks for copyright violations n n Use list of hashes

Copyright Crawler Web crawler looks for copyright violations n n Use list of hashes of all copyrighted content Scans all web sites, file-sharing networks, etc. For every music file found, compute hash and compare If match is found, call the lawyers Problems: n n n 10 Hash functions unlikely to exist for music Does not protect against anonymous postings: publius Very high workload

Examples Digi. Marc. Spider n n Crawls web looking for pirated images May use

Examples Digi. Marc. Spider n n Crawls web looking for pirated images May use watermarking? (next topic) MOSS (Measure Of Software Similarity) n n Detect plagiarism in programming assignments, web pages http: //www. cs. berkeley. edu/~aiken/moss. html SCAM: N. Shivakumar, Stanford. Crawls web looking for academic plagiarism n Several success stories: http: //www-db. stanford. edu/~shiva/SCAM/scam. Info. html n 11

Improvement: watermarking Embed hidden watermark at the recording studio n n Embed( M, I

Improvement: watermarking Embed hidden watermark at the recording studio n n Embed( M, I ): outputs a watermarked version of music M with the information I embedded in it Retrieve( M’ ): takes a watermarked music file M’ and outputs the embedded watermark I Watermark requirements (not necessarily achievable): Watermark must be inaudible (music) or invisible (video) n Watermark should be robust: Given M 1 = Embed(M, I), pirate cannot create an “acceptable” M 2 with Retrieve(M 2) I n w To do this, watermark must resist all signal processing tricks - resampling, cropping, low-pass filtering, … 12

Example Watermarked File Second image has watermark inserted by DOS software “White Noise Storm”

Example Watermarked File Second image has watermark inserted by DOS software “White Noise Storm” 13

Watermark-based enforcement Copyright crawler uses “Retrieve” algorithm Benefits: n n Copyright crawler does not

Watermark-based enforcement Copyright crawler uses “Retrieve” algorithm Benefits: n n Copyright crawler does not need list of all copyrighted material No need for content aware hash w Watermarking music “seems” to be an “easier” problem. But, some of the same problems as before n n n 14 Does not defend against anonymous postings High workload Need to mark with buyer or trace copy to culprit

Robust watermarks? ? Embed & Retrieve algs are usually kept secret n “Security by

Robust watermarks? ? Embed & Retrieve algs are usually kept secret n “Security by obscurity” – not a successful approach Do robust watermarking systems exist? n n We don’t know the answer Stir. Mark w Generic tool for removing image watermarks w Oblivious to watermarking scheme n SDMI challenge: w Broken: Felten, et al. 15 See: http: //cryptome. org/sdmi-attack. htm Obj 1 mark ? ? Obj 2 mark

Fingerprinting Basic idea: Embed a unique user ID into each sold copy n If

Fingerprinting Basic idea: Embed a unique user ID into each sold copy n If user posts copy to web or file-sharing network, embedded user ID identifies user n Problem: n n 16 Need ability to create distinct and indistinguishable versions of object Collusion: two users can compare their objects to find parts of the fingerprint

Watermarking Images (>200 papers) Digi. Marc: embeds creator’s serial number. n Add or subtract

Watermarking Images (>200 papers) Digi. Marc: embeds creator’s serial number. n Add or subtract small random quantities from each pixel. Embedded signal kept secret. Signafy (NEC). n n Add small modifications to random frequencies of entire Fourier Spectrum. Embedded signal kept secret. Caronni: Embed geom. shapes in background Sig. Num Tech. (Sure. Sign). 17

Watermarking Music (>200 papers) Aris Tech (Music. Code): n Rate: 100 bits/sec of music

Watermarking Music (>200 papers) Aris Tech (Music. Code): n Rate: 100 bits/sec of music Solana (E-DNA) n Merged to form Verance Used by SDMI Used by Liquid. Audio. Argent: Embed full text information. n Frame. Based: info. inserted at random areas of signal n Secret key determines random areas. n 18

“My Story” by Ed Felten Industry consortium (SDMI) considering four technologies for deployment in

“My Story” by Ed Felten Industry consortium (SDMI) considering four technologies for deployment in next-gen music and players. We (Princeton, Rice, Xerox researchers) study technologies, find that they don’t work very well. We write a paper detailing our findings. Paper accepted for publication at conference. 3 Slides from: http: //csrc. ncsl. nist. gov/ispab/2002 -06/Felten-06 -2002. pdf 19

“Our Paper” Music industry claims that our paper is a “technology” whose primary purpose

“Our Paper” Music industry claims that our paper is a “technology” whose primary purpose is copyright circumvention n Similar claim for oral presentation Threatens to sue authors of paper, conference organizers, and employers Seeks control over contents of paper 20

“My Story (cont. )” Music industry (RIAA, SDMI, Verance) threatens lawsuit if we publish

“My Story (cont. )” Music industry (RIAA, SDMI, Verance) threatens lawsuit if we publish n Conference organizers also threatened. We withdraw paper because of threats. We file lawsuit seeking right to publish After legal wrangling, paper is published We managed to publish, but: n n 21 Months of effort by researchers lost Hundreds of lawyer-hours spent ($$$) Member of our team loses his job Eight-month delay in release of our results

Outline Legal landscape Examine or modify content n n n Content hashing and copyright

Outline Legal landscape Examine or modify content n n n Content hashing and copyright crawling Watermarking Fingerprinting Regulate use through special content players n n Apply complex policies, need tamper-proof platform Some examples w w 22 Media. Max CD 3: restrict access for software players DVDs: CSS encryption and hardware/software players Windows Media Rights Management Office Information Rights Management

DRM Player threat model Traditional access control n Owner of computer sets discretionary access

DRM Player threat model Traditional access control n Owner of computer sets discretionary access controls DRM controls n Owner of content sets usage rights Player owned by “untrusted user” must enforce usage rights n Additional issue: copyright law allows fair use n 23

Passive vs Active Protection 24

Passive vs Active Protection 24

Media. Max CD 3 (Sunn. Comm) Goal n Restrict use of music CD on

Media. Max CD 3 (Sunn. Comm) Goal n Restrict use of music CD on computer Method n n CD contains autorun file that causes Windows to launch Launch. CD. exe, installs “Sbcp. Hid” driver Driver prevents copying of restricted CDs Failures n n Launch. CD. exe will not run on Linux On Windows: hold shift key while loading CD Digital Millennium Copyright Act (DMCA) n 25 Forbids circumvention of copy protection mechanisms, and circumvention tools and technologies http: //www. cs. princeton. edu/~jhalderm/cd 3/

Sony XCP CD contains copy protection software Copy protection software protected by rootkit Rootkit

Sony XCP CD contains copy protection software Copy protection software protected by rootkit Rootkit detected by Rootkit. Revealer 26 http: //www. sysinternals. com/blog/2005/10/sony-rootkits-and-digital-rights. html

Content protection via encryption Basic idea: n n n Content distributor encrypts content before

Content protection via encryption Basic idea: n n n Content distributor encrypts content before releasing it Release: C = EK[content] Decryption key embedded in all players. Player will only decrypt if policy is satisfied. Note: cannot prevent copying after decryption n n User can probe bus to sound card Unlike watermarking: watermark is embedded in content Propagates in cleartext copies of content Problem: what if one pirate uses reverse engineering to expose global key k ? ? 27

Example: CSS: Content Scrambling System n Used to protect DVD movies Each DVD player

Example: CSS: Content Scrambling System n Used to protect DVD movies Each DVD player manufacturer i has key Ki n n n 28 Embed same key Ksony in all players from Sony. Every DVD movie M is encrypted as follows: 1. enc-content = EK[M] where K is a random key 2. EKsony[k] , EKphilips[K] , … About 400 manufacturer keys

Problems with CSS De. CSS: n n n Extracted key from Xing software player

Problems with CSS De. CSS: n n n Extracted key from Xing software player Could decrypt any DVD playable on the Xing player MPAA revoked Xing key: disabled all Xing players! Bigger problem: n n n 29 Encryption algorithm in CSS is based on LFSR’s Very fast: video rate decryption on weak DVD player Very weak: given one manuf. key, can get all keys

Better revocation technique Embed a distinct key in every player Players: i Every node

Better revocation technique Embed a distinct key in every player Players: i Every node v has an associated key Kv. Every player corresponds to leaf node. Key for player i: all keys on path from root to leaf i. 30

Revocation Initially n n Encrypt all content with key at root Any player can

Revocation Initially n n Encrypt all content with key at root Any player can decrypt content. When player i is revoked n 31 Encrypt content-key so only players other than i can decrypt.

How to tell which player to revoke? When pirate publishes single key on Internet,

How to tell which player to revoke? When pirate publishes single key on Internet, MPAA knows which keys to revoke. What if pirate sells pirated players? n How can MPAA tell which keys embedded in player? Solution: Tracing systems can interact with player and determine how to revoke that player. n 32 How? Take crypto class…

Movies Books Music Digital Distribution Dream ( ) Artist Content Distributor Consumer Package Player

Movies Books Music Digital Distribution Dream ( ) Artist Content Distributor Consumer Package Player Content Package Content Software player 33 Secure network transactions

Digital rights management players Distribute information in specific format Player that knows this format

Digital rights management players Distribute information in specific format Player that knows this format controls action n n Control reading, playing, or copying content Guarantee payment in proportion to use w Count number of times content is used w Transfer payment to distributor No end run n n Must be impossible to use content without player Player must be tamper resistant Problem: Computer files are easy to duplicate Can software player on general-purpose computer achieve goals? 34

Two separate problems Attaching rights and making authorization decisions Enforcing decisions in a tamper-resistant

Two separate problems Attaching rights and making authorization decisions Enforcing decisions in a tamper-resistant software and hardware 35

Rosenblatt, et al. DRM Reference Architecture Content Server Content repository Product information DRM packager

Rosenblatt, et al. DRM Reference Architecture Content Server Content repository Product information DRM packager Financial transaction Rights License generator Package Encryption Content Metadata DRM controller Identities License Server 36 Rendering application Encryption Keys Encryption keys Client Rights License Identity

Windows Media Rights Manager Content owner Input file . wav, . mp 3, .

Windows Media Rights Manager Content owner Input file . wav, . mp 3, . avi Distributor License issuer Web site, CD, email message, etc encode Win Media file . wma, . wmv, . asf 37 Packaged Win Media file Key ID, license acquisition URL License Rights Windows Media License Service Packager package license URL Consumer (player) Packaged Windows Media file

Windows Key and License Management 38

Windows Key and License Management 38

Xr. ML Summary Vocabulary n n Principals: Alice, Bob Resources: movie, picture, song Rights:

Xr. ML Summary Vocabulary n n Principals: Alice, Bob Resources: movie, picture, song Rights: play, edit, print Properties: manager, employee, trusted Licenses and grants n license : : = (grant, principal) w Principal p issues/says grant g n grant : : = ∀x 1…∀xn (cond → conc) w If cond holds, then conc holds n conc : : = Pr(p) | Perm(p, r, s) w Pr(p) means principal p has property Pr w Perm(p, r, s) means p is permitted to exercise right r over resource s 39

HDCP, Secure Audio Path High-bandwidth Digital Content Protection n HDCP is a specification developed

HDCP, Secure Audio Path High-bandwidth Digital Content Protection n HDCP is a specification developed by Intel Corporation to protect digital entertainment content across the DVI/HDMI interface http: //www. digital-cp. com/home 40

Free. Me – breaks Windows Media RM http: //www. . com/crypt/drm/freeme/README The software distributed

Free. Me – breaks Windows Media RM http: //www. . com/crypt/drm/freeme/README The software distributed with this README file removes content protection from any Windows Media Audio file (. wma file) that uses DRM version 2 (as implemented in Windows Media Player version 7). … http: //www. . . com/crypt/drm/freeme/Technical This document describes version 2 of the Microsoft Digital Rights Management (MS-DRM), as applied to audio (. wma files). The sources for this material are varied. . . The basic components of MS-DRM involve use of elliptic curve cryptography (ECC) for public key cryptography, DES for a block cipher, RC 4 for a stream cipher, and SHA-1 for a hash function. There is also a block cipher which I haven't seen before, used in the MS-DRM system to build a MAC, or keyed hash function. 41

42 Q: Will users download “fix” if only player needs upgrade? (DRM threat model)

42 Q: Will users download “fix” if only player needs upgrade? (DRM threat model)

Further details Implementation Details: It is imperative to execute the following steps to neutralize

Further details Implementation Details: It is imperative to execute the following steps to neutralize the Freeme software breach… 1. Update the Content Header This procedure is performed by the organizations that package content. In this step the content packager will add an attribute … to the header of the protected Windows Media file. 2. Update the License Server(s) Each license issuer must update its license server configuration to ensure that: n It does not issue licenses to users who have the compromised security component on their PCs n It can issue licenses to users who have updated the security component on their PCs. NOTE: if the license server is not updated (with the steps above) and an updated client (a client that has been updated with the new security component) makes a request to the license server, the license server will fail and generate an error to the client. 3. Trigger update of the new security component on the server side This step updates the license server so it can detect the version number of the DRM security component that is making the license request, and redirect it to an upgrade Web page if the security component version is less than "2. 2. 0. 1". 43 http: //www. microsoft. com/windowsmedia/forpros/drm/freeme. aspx

Continuing controversy over DRM… 44

Continuing controversy over DRM… 44

Microsoft Office Rights Management 45

Microsoft Office Rights Management 45

Apple’s Fair. Play Technology Restricts playing, recording, sharing of files n n n Allows

Apple’s Fair. Play Technology Restricts playing, recording, sharing of files n n n Allows media to be shared among devices Allows others to listen to (but not copy) music Can burn audio CD, eliminates DRM protection How it works (overview) n n i. Tunes uses encrypted MP 4 audio files Acquire decryption key by trying to play song w player generates a unique ID, sends ID to i. Tunes server w if not over authorization limit, server sends decryption key n 46 Decryption key is encrypted in i. Tunes to prevent transfer to another machine

i. Tunes Accounts and Authorizations Prior to buying content from i. Tunes Store n

i. Tunes Accounts and Authorizations Prior to buying content from i. Tunes Store n n n 47 User creates an account with Apple's servers and then authorizes a PC or Mac running i. Tunes creates a globally unique ID for device, sends to server, assigned to user's i. Tunes account Five different machines can be authorized. www. roughlydrafted. com/RD/RDM. Tech. Q 1. 07/. . .

Buying and playing songs When a user buys a song n n n A

Buying and playing songs When a user buys a song n n n A user key is created for the purchased file Encrypted using master key included in protected song file Master key encrypted with user key, held by i. Tunes and server Playing a song n n 48 i. Tunes does not need to connect to server i. Tunes has keys for all tracks in its library

Additional user devices When a new computer is authorized n n n 49 it

Additional user devices When a new computer is authorized n n n 49 it generates a globally unique ID number Stores ID on Apple server (up to 5 devices) Server sends new machine entire set of user keys for all the tracks purchased under the account

Cracking i. Tunes “DVD John” Discovered attacks while building i. Tunes client for Linux:

Cracking i. Tunes “DVD John” Discovered attacks while building i. Tunes client for Linux: n QTFair. Use grabs song data w After unlocked and uncompressed by i. Tunes, dumps raw stream into container file, n VLC media player, Play. Fair, Hymn, JHymn w intercept unlocked but not yet uncompressed song files, creating a small, ready to play, unencrypted AAC file. n Py. Musique, a Linux client for the i. Tunes Store w requests songs from Apple servers and downloads them without locking them n 50 Fair. Keys simulates i. Tunes client w requests a user keys from server, unlocks purchased songs

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