United States Patent [191
`Auerbach et al.
`
`1
`
`‘
`
`US005673316A
`
`‘
`
`1
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,673,316
`Sep. 30, 1997
`
`[54]
`
`CREATION AND DISTRIBUTION OF
`CRYP’I‘OGRAPHIC ENVELOPE
`
`9/1996 Ross et a1. .............................. .. 380/25
`5,553,143
`5,586,186 121996 Yuval et a1. .............................. .. 380/4
`
`[75]
`
`Inventors: Joshua Seth Auerbach. Ridge?eld.
`Conn.; Chee-Seng Chow. Cupertino,
`Calif.; Marc Adam Kaplan. Katonah,
`N.Y.; Je?'rey Charles Crigler. McLean,
`Va.
`
`[73]
`
`Assignee: Intemational Business Machines
`Corporation. Armonk, NY.
`
`[21]
`[22]
`[5 1]
`[52]
`[5 3]
`
`[56]
`
`Appl. No.: 625,475
`Filed:
`Mar. 29, 1996
`
`Int. CT.6 ...................................................... .. H04L 9/00
`US. Cl. ..... ..
`380/4; 380/25
`Field of Search ............................. .. 380/3, 4, 23, 24,
`380/25, 28. 49
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`6/1994
`5,319,705
`5,394,469 2/1995
`5,416,840
`5/1995
`5,428,685
`6/1995
`5,490,216
`2/1996
`5,509,070
`4/1996
`5,530,752
`6/1996
`
`Primary Examiner-David C. Cain
`Attorney, Agent, or Firm—Douglas W. Cameron
`[57]
`ABSTRACT
`
`A method and apparatus to create, distribute. sell and control
`access to digital documents using secure cryptographic
`envelopes. An envelope is an aggregation of information
`parts. where each of the parts to be protected are encrypted
`with a corresponding part encryption key. These encrypted
`information parts along with the other information parts
`become part of the envelope. Each part encryption key is
`also encrypted with a public key. and these encrypted part
`encryption keys are also included in the envelope. The
`envelope also includes a list of parts where each entry in the
`list has a part name and a secure hash of the named part. The
`list is then signed with a secret key to generate a signature.
`which is also included in the envelope. The signature can be
`veri?ed using a second public key associated with ?rst secret
`key. and the integrity of any information part in the envelope
`can be checked by computing a second hash and comparing
`it with the corresponding hash in the list of parts. Also, the
`information content of any encrypted part can only be
`recovered by knowledge of a second secret key correspond
`ing to the public key that was used to encrypt the part
`encryption keys.
`
`8 Claims, 6 Drawing Sheets
`
`CLEAR TEXT "TEASER"
`
`201
`
`/-205
`
`ENCRYPTED DOCUMENT PART
`
`204
`
`ENCRYPTED CONTROL PART
`
`v205
`ENcRYPTEO FINGERPRlNTlNG &
`WATERMARKING INSTRUCTIONS
`/206
`TERMS AND CONDITIONS
`
`-202
`
`ENcRYPTEO
`PEK
`
`//21O
`ENCRYPTED
`PEK
`
`/zn
`ENcRYPTEO
`PEK
`
`F _______ __
`
`_ _ _ _ _ _ _ _ __ C227.
`
`I
`
`:
`,
`l
`:
`I
`{
`l
`l
`I
`l
`
`LIST OF PARTS
`(PART NAME & SECURE HASHES)
`
`209'
`
`SiGNATURE ON LIST OF PARTS
`
`80M
`
`\\
`2
`08
`
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`l
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`h _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____|
`
`22°
`
`Petitioner Apple Inc. - Exhibit 1013, p. 1
`
`

`

`US. Patent
`
`Sep.30, 1997
`
`Sheet 1 of 6
`
`5,673,316
`
`/102
`
`BS
`(BUY
`SERVER)
`
`STEP 4
`
`103
`
`CRYPTOLOPE
`
`0s
`(DOCUMENT
`SERVER)
`
`USER PC
`
`STEP 5
`
`DFWM
`SECURITY
`BOUNDARY
`
`FIG. 1
`
`Petitioner Apple Inc. - Exhibit 1013, p. 2
`
`

`

`US. Patent
`
`Sep. 30, 1997
`
`Sheet 2 of 6
`
`5,673,316
`
`CLEAR TEXT "TEASER’
`
`201
`
`K203
`
`ENCRYPTED DocUMENT PART
`
`/ 202
`ENCRYPTED
`PEK
`
`ENCRYPTED CONTROL PART
`
`CRYPTED
`EN PEK
`
`205
`
`21 1
`
`ENCRYPTED FINGERPRINTING &
`WATERMARKING INSTRUCTIONS
`
`ENCRYPTED
`PEI<
`
`20s
`
`TERMS AND CONDITIONS
`
`209
`
`l
`:
`I
`|
`l
`I
`l
`:
`I
`'
`l L
`
`SIGNATURE 0N LIST OF PARTS
`
`________________________ "5291
`l
`LIST OF PARTS
`}
`(PART NAME & SECURE HASHES)
`I
`.
`l
`l
`I
`l
`}
`l
`l
`J
`
`BOM
`
`22.0
`
`208
`
`Petitioner Apple Inc. - Exhibit 1013, p. 3
`
`

`

`US. Patent
`
`Sep. 30, 1997
`
`Sheet 3 0f 6
`
`5,673,316
`
`BOM
`
`LIST OF PARTS
`
`207 /
`
`/209
`
`PART NAME
`
`MD5 OF PART
`
`302
`
`A ABSTRACT
`
`13ABDF77F...~
`
`501
`
`ENCRYPTED DOC
`PART 1
`
`24FDEC234...
`
`ENCRYPTED PEK 3
`
`A56FFE67...
`
`TERMS & CONDTIONS
`
`13FCD457...
`
`SIGNATURE ON LTST OF PARTS
`
`DOCUMENT SERVER’S SECRET KEY
`ENCRYPTION OF MDS OF LIST OF PARTS
`\
`\ZOB
`
`FIGS
`
`Petitioner Apple Inc. - Exhibit 1013, p. 4
`
`

`

`US. Patent
`
`Sep. 30, 1997
`
`Sheet 4 of 6
`
`5,673,316
`
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`
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`
`Petitioner Apple Inc. - Exhibit 1013, p. 5
`
`Petitioner Apple Inc. - Exhibit 1013, p. 5
`
`
`
`

`

`US. Patent
`
`Sep. 30, 1997
`
`Sheet 5 of6
`
`5,673,316
`
`LIST OF ARTICLES TO BUY
`
`LAP-501 '
`
`USER CREOENTIALS AND USER
`AUTHENTICATION RELATED INFO
`
`202
`
`/_502
`I
`
`SOS
`
`ENCRYPTEO
`PEK
`
`ENVIRONMENTAL
`VARIABLES
`
`DFWM
`PUBLIC KEY \BOA
`
`/205
`ENCRYTEO FINGERPRINTING AND
`WATERMARKING INSTRUCTIONS
`
`ENCRYPTEO fen
`PEK
`
`TERMS AND CONDITIONS
`
`/'206
`
`I'- — — _ _ _ * _ * _ _ _ _ _ _ _I
`
`|
`I
`1
`:
`L
`
`LIST OF PARTS
`(PART NAME & SECURE HASHES)
`
`SIGNATURE ON LIST OF PARTS
`BOM
`
`209
`/|/
`P207
`I
`208
`T
`_|
`
`AUTHENTICATION & INTEGRITY CHECKINGS
`
`/"'505
`
`BUY REQUEST MESSAGE (BRM)
`
`500
`
`Petitioner Apple Inc. - Exhibit 1013, p. 6
`
`

`

`U.S. Patent
`
`Sep. 30, 1997
`
`Sheet 6 of 6
`
`5,673,316
`
`601
`
`600
`
`ACTUAL PURCHASE PRICE
`
`602
`
`603
`
`TRANSLATED PEK ———
`DECRYPTED, RE-ENCRYPTED
`AT BS
`
`TRANSLATED PEK -———
`DECRYPTED, RE-ENCRYPTED
`AT 55
`
`ECRYPTED CUSTOMIZED FINGERPRINTING
`AND WATERMARKING INSTRUCTIONS-""
`DECRYPTED,CUSTOMIZED,RE-ENCRYPTED AT BS
`
`604
`
`TRANSFORMED TERMS AND CONDITIONS
`-——-— EVALUATED AT BS
`
`605
`
`AUTHENTICATION & INTEGRITY RELATED CHECKS
`
`BUY SERVER RESPONCE (BSR)
`
`\
`
`FIG.6
`
`606
`
`Petitioner Apple Inc. - Exhibit 1013, p. 7
`
`

`

`5,673,316
`
`1
`CREATION AND DISTRIBUTION OF
`CRYPTOGRAPHIC ENVELOPE
`TECHNICAL FIELD
`This invention describes a method for the creation.
`distribution. and sale and for the controlled access of digital
`documents using the methods and techniques of secure
`cryptographic envelopes.
`BACKGROUND OF THE INVENTION
`Digital documents have numerous advantages over paper
`based. analog documents. They are easier to create.
`distribute. and duplicate. However, these advantages also
`make it di?icult to protect their associated intellectual rights
`from infringements. Nevertheless. digital documents will
`replace paper-based documents as a vehicle for the distri
`bution and sale of information in the future.
`(ID-Showcase (US. Pat. No. 5.319.705)
`An important distinction between our work and the
`CD-showcase patent [2] is that in our invention the part
`encryption key is carried in the cryptographic envelope and
`is encrypted under a public key. Whereas in CD-Showcase.
`the distributed data only contains an identi?er of the encryp
`tion key. The encryption key is stored at a server and is
`retrieved upon the presentation of the key identi?er.
`Thus. with the CD-showcase patent. it is necessary to
`maintain a key database at the server necessitating a measure
`of trust between a buy server and a document server.
`PGP (Pretty Good Privacy) PGP [3] is a public-key based
`system for sending secure e-mail. The body of the e-mail is
`encrypted using an lDEA algorithm (see. e.g.. [1]). and the
`encryption key is encrypted using the public key of the
`intended recipient. Both the encrypted e-mail text and the
`encrypted encryption key are sent. The recipient uses his
`secret key to recover the encryption key, which is then used
`to recover the plain text
`
`20
`
`25
`
`2 .
`the distribution of bulk data and (2) the controlled release of
`content through the release of PEKs.
`This invention extends on this basic concept and intro
`duees the techniques of cryptographic envelopes for content
`distribution and sale. Furthermore. the concepts and tech
`niques are generalized to handle arbitrary terms and condi
`tions on the access to and use of digital documents. The
`generalization allows cryptographic envelope to be used as
`a basis for designing and implementing distributed access
`control of digital documents.
`This invention makes it unnecessary to maintain such a
`key database at the server and furthermore allows a cleaner
`separation of trusts between the Document Server (place
`where contents are encrypted) and the Buy Server (place
`where document encryption keys can be obtained).
`Accordingly. this invention provides a method of creating
`a cryptographic envelope which can be distributed arbi
`trarily to any number of users. where only authorized users
`have access to the clear text content of the secure informa
`tion parts. With this invention. each of the information parts
`is encrypted with a corresponding part encryption key to
`generate an encrypted information part. Each part encryp
`tion key is then encrypted with a public key. A list of parts
`that are included in the envelope is also created, and each
`entry in the list has a part name and a secure hash of the
`named part. The envelope. then. includes the encrypted
`information parts. the unencrypted information parts. the
`encrypted part encryption keys and the list of parts. Finally.
`the list of parts is signed with a secret key to produce a
`signature. and this signature is also included in the envelope.
`The integrity of the list can be checked using a second public
`key associated with the secret key that was used to sign the
`list. The integrity of any one information part can be checked
`by computing a second hash on the part and comparing the
`second hash with the corresponding hash for the part in the
`list. Finally the information content of the encrypted part is
`protected from disclosure and can only be recovered with a
`part encryption key, and knowledge of a secret correspond
`ing to a public key is necessary to obtain an unencrypted part
`encryption key. The latter unencrypted key is then used to
`generate clear text from the information part.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 gives an overview of the ?ve steps of a crypto
`graphic envelope process. The main entities involved in the
`process are the Document Server (DS) 100. the Buy Server
`(BS) 102. the decryption ?ngerprinting and watermarking
`module (DFWM) 103. and user pmsonal computer (UPC)
`101.
`FIG. 2 shows the structure of a typical cryptographic
`envelope. The minimal elements are an encrypted part 203
`and its associated entrypted part encryption key (PEK) 202.
`list of parts 209. and signature of list of parts 208.
`FIG. 3 shows the structure of a bill of materials (BOM).
`which has a list of parts 209. Each entry of the table contains
`the part name 302, e.g.. “Abstract". and the MessageDigestS
`(MDS), that is. a secure hash, of the named part 301. e.g,
`“13ADBF77F . . . ". The MDS of the list is computed and
`the resultant hash is signed using the DS’s secret key to
`produce a digital signature 208. The list 209 and the signa
`ture 208 form the DOM.
`FIG. 4 shows a typical price matrix. The columns shows
`the discount factor for various membership categories (402,
`403, 404. 405), and the rows show the quantity discount
`(406, 407. 408. 409). A sample formula for computing the
`price of the n-th copy and the total price of 11 copies is as
`shown 401.
`
`SUMMARY OF THE INVENTION
`This invention describes a method for the creation,
`distribution. and sale of digital information using the meth
`ods and techniques of secure cryptographic envelopes.
`Cryptographic envelopes use modern cryptographic tech
`niques (such as encryption and authentication) to secure
`document parts from unauthorized reading and tampering.
`The process described in this disclosure allows parts of a
`cryptographic envelope to be bought by a user and their
`informational contents released in a secure and controlled
`manner. Additional processing of the parts are introduced to
`deter piracy. Furthermore. the use of public-key technology
`makes cryptographic envelope technique a convenient.
`secure. and self-contained means of distributing digital
`information.
`Super distribution
`The basic model for information distribution assumed
`here is super distribution. (See [5} for a more in-depth
`discussion on the subject.) The basic idea is that digital
`documents (or parts) can be freely distribution over the
`Internet, by radio or television signals. by cable. by satellite,
`by local area networks, by diskettes. by CD-ROMs. and by
`BBS as long as each document is encrypted Assuming that
`the encryption process is su?iciently secure, the only way a
`user can have access to the content is to purchase the
`necessary PEKs (part encryption keys) that are typically
`orders of magnitudes more compact than the documents they
`decrypt.
`Super distribution is a powerful concept because it
`decouples the problem of information distribution into ( 1)
`
`50
`
`65
`
`Petitioner Apple Inc. - Exhibit 1013, p. 8
`
`

`

`5,673,316
`
`3
`FIG. 5 shows a Buy Request Message (BRM) 500.
`Included in the BRM are the encrypted PEKs (202. 211).
`encrypted ?ngerprinting and watermarking instructions 205.
`terms and conditions 206. and BOM 207. Items 202. 205.
`206. 207. and 211 are copied from the cryptographic enve
`lope 200 (see FIG. 2). The other parts of the BRM (501-505)
`are generated at the UPC.
`FIG. 6 shows a Buy Server Response (BSR) 600. The Buy
`Server (BS) translates the PEKs to produce translated PEKs
`(602. 603) which only the DFWM 103 can decrypt. The
`?ngerprinting and watermarking instructions are decrypted.
`customized. and re-encrypted. and the result 604 can be
`decrypted only by the DFWM. The terms and conditions in
`the BRM (500. FIG. 5) are also evaluated and may produce
`updated or transformed terms and conditions 605. The actual
`purchase price 601 is computed by applying the appropriate
`discounts on the base price.
`
`10
`
`4
`and (2) there should be means of associating di?ierent parts.
`e.g.. by naming. pointers. or indices.
`Information parts are of two types: document (201 and
`203) and control (202. 204-211). Document parts are the
`“contents". Some examples of document parts are abstracts.
`table of contents. ?gures. tables. and texts. They could also
`be portions of an executable program. a library of
`subroutines. software modules. or object components.
`Referring to FIG. 2. document parts may be encrypted
`(203). Encrypted document parts 203 are often the “valuable
`contents” to be purchased by the user (e.g.. a section of a
`book. a high resolution JPEG picture. or an MPEG stream).
`Unencrypted parts are the “teasers” 201 (e.g.. reviews of the
`book by others. the table of content. the abstract. or a low
`resolution IPEG picture). The purpose of the unencrypted
`parts is to allow the user to “preview”. "sample”. or
`“browse” the contents of a cryptographic envelope before
`the actual purchase.
`Some pre-processing. such as compression and insertion
`of special string patterns. may be applied to document parts.
`Compression reduces storage. Other pre-processing are
`modi?cation to the document parts to facilitate the ?nger
`printing and watermarking of document parts by the
`DFWM.
`Connrol parts are the metadata needed to support the
`functions and the process model of a cryptographic enve
`lope. There are two main funciions: authenticity and con?
`dentiality. The of the cryptographic envelope are not tam
`pered with. This authentication function is achieved by using
`digital signatures. The con?dentiality function is achieved
`by encryption (e.g.. using DES or IDEA). The basics of
`these encryption and authentication techniques are well
`known in the art and can be found in any modern text on
`cryptography (e.g, see [1]). All control parts are authenti
`cated and some may be encrypted. if necessary.
`Examples of control parts are price matrix (See FIG. 4.
`400) and ?ngerprinting and watermarking instructions 205
`for the post-processing of the document parts. The post
`processing of the document parts is performed by the
`DFWM. when the cryptographic envelope is open. Finger
`printing and watermarking are examples of post-processing,
`they mark document parts in a way to deter piracy.
`Referring to FIG. 4. The price matrix 400 describes the
`pricing structure for the purchase of the document parts, e.g..
`volume discount for buying multiple copies. discount for
`club membership, or corporate discount An example for
`mula 401 to compute the purchase price of 11 copies of a
`document. (Note. the price discount factor may also be time
`dependent. in which case the columns of the price matix
`(402-405) are time-limited special offers instead of club
`membership.)
`Referring to FIG. 2. terms and conditions 206 on the
`purchase and the use of the document parts can also be
`included in the cryptographic envelope. They may be
`included as document parts (in which case they will be made
`visible to the user) or included as control parts (in which
`case they will be evaluated at the Buy Server (BS) 102 and
`possibly again at the user's personal computer (UPC) 101).
`The document parts contain some textual infonnation. and
`the control parts may contain some program (e.g.. written in
`a scripting language such as Perl [4]) implementing the
`terms and conditions. (Note: The ?ngerprinting and water
`marking instructions. and the price matrix. We list them
`explicitly for clarity.)
`Con?dentiality and Authenticity
`We now describe a method in which con?dentiality can be
`achieved. Parts of value are encrypted using a DES (Data
`
`20
`
`25
`
`35
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`Referring to FIG. 1. one of the key advantages of the
`cryptographic envelope process is security. It is assumed that
`the BS (Buy Server) 102 and the DS (Document Server) 100
`are secure. E.g.. they are managed and owned by the
`respective business partners in the enterprise and are oper
`ated by trusted personnel inside a glass house.
`It is also assumed that there isn’t much security at the
`UPC (User Personal Computer) 101. since it belongs to the
`user, except that it has a relatively small and secure DFWM
`(Decryption Fingerprinting and Watermarking Module) 103.
`where security is provided in software or through tamper
`resistant hardware.
`Overview of Steps
`An overview of the processing steps is as follows. (See
`FIG. 1.)
`Step l-Cryptographic Envelope Creation
`Step 2-Cryptographic Envelope Distribution
`Step 3-User-Initiated Buy Request
`Step 4-Buy Server Response
`Step S-Opening of Cryptographic Envelope
`Cryptographic Envelope Processing Steps
`Each of these processing steps is described in greater
`details.
`Step 1: Cryptographic Envelope Creation
`The ?rst step is the creation of a cryptographic envelope.
`See 200 of FIG. 2. The creation event is usually done o?lline
`by the content provider because of anticipated needs for a
`collection of digital documents to be super distributed.
`Alternatively, it could be triggered by a user request. In
`this case the a'yptographic envelope would be created
`speci?cally for the user. and the cryptographic envelope may
`contain certain information speci?c to the user or the
`request. Moreover, if it's anticipated that there will be
`similar future requests by other users. additional information
`might be included in the cryptographic envelope. and the
`cryptographic envelope is cached to allow future similar
`requests to be ful?lled more e?iciently.
`Cryptographic Envelope Parts
`A cryptographic envelope is a grouping of information
`parts. See 201-211 of FIG. 2. Some of the information parts
`are encrypted while others are in clear text. The crypto
`graphic envelope process is compatible with a wide vm'iety
`of grouping technologies (e.g. zip. tar, and the more object
`oriented approaches of OpenDoc Bento and Microsoft
`0113). The requirements on the grouping method is minimal:
`(1) the parts can be aggregated into a unit suitable for
`distribution and the parts can later be individually retrieved.
`
`45
`
`55
`
`65
`
`Petitioner Apple Inc. - Exhibit 1013, p. 9
`
`

`

`5
`
`20
`
`25
`
`30
`
`5
`Encryption Standard) algorithm (e.g.. see [1]). Different
`parts are encrypted using diiferent PEKs (part encryption
`keys). These keys are chosen randomly and independently.
`There are many ways of generating a random encryption
`key. One way is to use random or a pseudo-random number
`generator to produce a random string. which is used as the
`key. More details on these scheme can be found in [1.3].
`Each PEK is encrypted using the public key of a BS (Buy
`Server) 102 and the resultant encrypted PEK 202 (FIG. 2)
`becomes a control part in the cryptographic envelope: (Note:
`a PEK may be encrypted using di?erent BS public keys and
`all theses encrypted PEKs included in the cryptographic
`envelope.)
`There are many ways of ensuring the authenticity of a
`cryptographic envelope and its parts. We now describe one
`such method. Every cryptographic envelope has a special
`control part called BOM (Bill of Materials) 207. The BOM
`is consist of two parts: (1) a list of parts 209. and (2) a digital
`signature 208.
`We apply a secure hash function. MessageDigestS (MDS)
`(see. e.g.. [l] for details). to each part included in a cryp
`tographic envelope and create a list. Referring to FIG. 3.
`each entry in the list contains the part name or reference 302
`and a secure hash 301 of the information part corresponding
`to the part name. (E.g.. In the case of a ?le-based grouping.
`list of parts would be a ?le containing the ?le names of all
`the ?les and their corresponding hash results.)
`The list is then digitally signed with a secret key known
`only to the DS (Document Server) 100. There are many
`ways of digitally signing a document (see. e.g.. [1]). One
`way is to compute the MDS (or any other secure hash) of the
`list of parts and to encrypt the resultant hash using the secret
`key (to produce a signature) 208. The list of parts and the
`signature together are referred to as the BOM 207. Note. that
`only the public key of the DS is needed to verify the
`authenticity of the BOM.
`Authenticity of the cryptographic envelope is checked by
`decrypting the signature using the public key of the DS and
`comparing that with the MDS of list of parts. If the two
`match, then the list of parts has not been tampered with. The
`authenticity of individual parts can also be checked by
`computing the MDS of the each part. and by comparing the
`result its corresponding entry in the list. Therefore. the BOM
`207 ensures the integrity of a cryptographic envelope and all
`its parts.
`Cryptographic Envelope is Self-Contained
`An important feature of cryptographic envelope is that it
`is self-contained in the following sense. Only the public key
`of a DS is needed to verify the authenticity of the crypto
`graphic envelope. Because the encrypted PEKs (202. 210.
`211. see FIG. 2) are with the cryptographic envelope. only
`the secret key of a BS is needed recover the content.
`Moreover, di?erent Document Servers can generate crypto
`graphic envelopes using only the public key of the BS; no
`other communications between 138s and DSs are needed.
`Cryptographic Envelope Creation Steps
`We now summarize the processing steps in the creation of
`a cryptographic envelope. (See FIG. 2)
`1-a—-Assemble information parts to be included in the
`cryptographic envelope.
`l-b—-Apply optional processing steps (e.g.. compression.
`pre-?ngerprinting. and pre-watermarking) to parts.
`Keep su?icient state information of these processing
`steps to undo the operations later.
`l-c-Generate random PEKs (part encryption keys) 202.
`one for each part to be encrypted.
`l-d-Encrypt document parts with their respective PEKs
`to form the encrypted parts (203. 204. 205). which are
`included in the cryptographic envelope.
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`l-e-—The PEKs are then encrypted using the public key of
`a BS to form encrypted PEKs (202. 210. 211). which
`are included in the cryptographic envelope. Encrypted
`PEKs and their corresponding encrypted parts are asso
`ciated.
`1-f—Also encrypt the instructions and other state infor
`mation from Step l-b using some random PEKs. The
`PEKs are encrypted with a public key of the BS. Both
`encrypted parts (203. 204. 205) and encrypted PEKs
`(202. 210. 211) are placed in the cryptographic enve
`lope.
`l-g-Include in the cryptographic envelope clear text
`parts such as “teasers‘i abstracts. and a table of content
`201.
`1-h—Include terms and conditions such as ?ngerprinting
`and watermarking instructions 205 and pricing matrix
`206. Encrypt any parts or sub-parts if necessary (and
`include their encrypted PEKs). As before associate
`encrypted parts with their encrypted PEKs.
`l-i—Create a list 209 of information parts. listing all the
`parts assembled and computing a secure hash for each
`of the parts listed.
`1-j—Create a signature 208 for BOM 207 by digitally
`signing the list. e.g.. computing the secure hash of the
`list and encrypting it with the DS secret key. The BOM
`207 (list 209 and signature 208) are added to crypto
`graphic envelope.
`See FIG. 2 for details on possible cryptographic envelope
`structure.
`Step 2: Cryptographic Envelope Distribution
`Once a cryptographic envelope is created. it can be
`distributed by any means. e.g.. sending over the Internet. by
`radio or television signals. by cable. by satellite. by
`CD-ROMs. and by BBS. Security of distribution is not
`needed. Cryptographic envelopes may be copied.
`duplicated. and shared between users. In fact. it’s our
`anticipation that “down-stream” distribution of crypto
`graphic envelope (i.e.. copying cryptographic envelope by
`friends) is a cost-elfective means of distributing crypto
`graphic envelope. Lastly. cryptographic envelope may be
`stored in any servers without any security requirement on
`the server.
`Step 3: User-Initiated Buy Request
`This step is often preceded by a user browsing the plain
`text “teaser” 201 portion of a cryptographic envelope. A user
`who is interested in the cryptographic envelope content
`would have to buy the necessary PEKs from the BS. (See
`FIG. 1.)
`Graphical User Interface
`The browsing of the cryptographic envelope is performed
`with the help of a GUI such as a modi?ed web browser that
`understands the cryptographic envelope structure. First. the
`modi?ed browser must be able to check the integrity of the
`cryptographic envelope. The user is noti?ed of any tamper
`ing of the cryptographic envelope parts through the integrity
`check. Next. the browser should be able to display the clear
`texts in the cryptographic envelope. e.g.. display the
`abstracts and table of contents. Finally. referring to FIGS. 2
`and 5. the browser must the able to extract the necessary
`parts from the cryptographic envelope 200 to construct a
`BRM (Buy Request Message) 500.
`Prior Registration
`We assume that there was a prior registration step carried
`out by the user so that the user is recognized by the BS. For
`example. the user could register with a trusted third party.
`For example. the registration may involve a phone call
`from the user to a registration center which will issue an
`
`Petitioner Apple Inc. - Exhibit 1013, p. 10
`
`

`

`7
`account number to the user. The account number is then
`forwarded to all the 1385. Alternatively. the registration
`center can digitally sign the account number; in which case.
`no update in the 138s is needed. A BS can just verify the
`account number by checking the signature.
`After registration. the user is issued certain credentials
`(e.g.. account number and other membership information). A
`credential is a document digitally signed by a trusted third
`party which contains information such as an account
`number. a?liations. or rights held by the user also, as an
`example. the third party could issue to the user certain “book
`clu ” membership credentials that entitles him to discounts
`olf the list price.
`Secure DFWM
`More speci?c to our methods is that we assume. as a result
`of registration. a secure DFWM (103. FIG. 1) (decryption
`?ngerprinting watermarking module) is instantiated at the
`UPC
`The DFWM is responsible for decrypting the parts and at
`the same time applying ?ngerprinting and watermarking on
`the decrypted parts. Watermarking puts visible markings in
`the document in such a way that is hard to erase and does not
`atfect the perusal of the document. Fingerprinting are “invis
`ible” markings in the document and are therefore hard to
`remove.
`For more information on ?ngerprinting and watermarking
`techniques. see application Ser. No. 08/494615 ?led on Jun.
`2%. 1995. and assigned to the same assignee of the instant
`application.
`Instantiation of DFWM
`There are various implementations of a secure DFWM.
`The sirnpliest is based on the public key techniques. where
`the DFWM securely generates and stores a secret key within
`the DFWM security boundary. For example, the DFWM
`could use a pseudo-random number generator to create a
`35
`public-secret key pair. The DFWM secret key is stored
`within the DFWM and the public key is lmown to the
`outside. The registration process allows the trusted third
`party to certify the DFWM public key. (See e.g.. [1] on
`public key certi?cation process.) The DFWM secret key is
`the only secret information kept in the DFWM module.
`Security of DFWM
`The DFWM could be a piece of software running in a
`physically secured module (e.g. smart cards) or running in
`the UPC environment (which is unsecure). In the former
`case. security is achieved through the physical tamper resis
`tance of the packaging. Cm'rent packaging technology can
`provide suf?cient security to the DFWM for all practical
`P"IP°5¢$
`We will focus on the latter case, where we do not assume
`the physical security of DFWM. This is the more interesting
`case. since the availability of physical security only
`enhances the security of DFWM.
`Without secure hardwares. the security of DFWM cannot
`be guaranteed. In many practical cases. we can achieve
`su?icient security using well-known software techniques
`(e.g., code-obscuring techniques well known to virus
`writm's).
`However. one of key advantages of the process described
`in this disclosure is that even if the DFWM is compromised.
`the exposure is
`The user cannot unlock a document
`part that hadn't been purchased (since the PEK is not
`available). The buy transaction is secure since it must go
`through a secure BS.
`If a DFWM is compromised (e.g.. the DFWM secret key
`is exposed). the only possible loss is that a document that a
`user purchased is not properly ?ngerprinted and water
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`marked. However. the security risk is not entirely dilferent
`from the possibility of the user erasing the markings from
`the document.
`Buy Request Transaction
`We now describe the buy request transaction in greater
`detail.
`Through the Graphical User Interface (GUI). the user is
`prompted with a list of articles contained in the crypto
`graphic envelope. The user may browse the relevant
`abstracts for more information. The user may also know the
`list price of the articles. If the user still wants to buy the
`articles. the user would initiate a buy-request through the
`GUI. resulting in a BRM (Buy Request Message) (see 500,
`FIG. 5) being sent to the BS 102.
`User Authentication
`Before the buy request can be completed. the system may
`want to authenticate the user. There are many well known
`techniques for user authentication by the system. E.g.. one
`such technique (similar to what is used in Pretty Good
`Privacy [3]) is to store the user private key encrypted on the
`disk drive of the UPC.
`The user is prompted for his password. which is used to
`decrypt the private key. The private key is used to digitally
`sign or certify a buy~related message and is erased at the end
`of each session.
`Environmental variables
`Environmental variables are information about the user
`environment or information about the UPC (e.g., locale.
`time. machine type. operating system name. etc.). In
`contrast. user credentials are information about the user.
`Environmental variables are of two types: secure and
`insecure. Secure variables are verified and digitally signed
`They can be checked and signed either by the BS (dln'ing
`registration) or generated and signed by the DFWM.
`Insecure variables are generated by the UPC. They are not
`veri?ed or signed They are included solely for informa
`tional purposes. Throughout this document. environmental
`variables will mean both.
`Buy Request Message
`Referring to FIG. 5, the BRM 500 contains the following
`information copied or extracted ?'om the cryptogra