DE19511298B4 - Procedure for issuing and revoking the authorization to receive broadcasts and decoders - Google Patents

Procedure for issuing and revoking the authorization to receive broadcasts and decoders

Info

Publication number
DE19511298B4
DE19511298B4 DE1995111298 DE19511298A DE19511298B4 DE 19511298 B4 DE19511298 B4 DE 19511298B4 DE 1995111298 DE1995111298 DE 1995111298 DE 19511298 A DE19511298 A DE 19511298A DE 19511298 B4 DE19511298 B4 DE 19511298B4
Authority
DE
Germany
Prior art keywords
decoder
keys
key
node
assigned
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
DE1995111298
Other languages
German (de)
Other versions
DE19511298A1 (en
Inventor
Jörg Dr.rer.nat. Schwenk
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deutsche Telekom AG
Original Assignee
Deutsche Telekom AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Deutsche Telekom AG filed Critical Deutsche Telekom AG
Priority to DE1995111298 priority Critical patent/DE19511298B4/en
Publication of DE19511298A1 publication Critical patent/DE19511298A1/en
Application granted granted Critical
Publication of DE19511298B4 publication Critical patent/DE19511298B4/en
Anticipated expiration legal-status Critical
Application status is Expired - Lifetime legal-status Critical

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04HBROADCAST COMMUNICATION
    • H04H60/00Arrangements for broadcast applications with a direct linking to broadcast information or broadcast space-time; Broadcast-related systems
    • H04H60/09Arrangements for device control with a direct linkage to broadcast information or to broadcast space-time; Arrangements for control of broadcast-related services
    • H04H60/14Arrangements for conditional access to broadcast information or to broadcast-related services
    • H04H60/23Arrangements for conditional access to broadcast information or to broadcast-related services using cryptography, e.g. encryption, authentication, key distribution
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00Cryptographic mechanisms or cryptographic arrangements for secret or secure communication
    • H04L9/08Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0819Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
    • H04L9/083Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
    • H04L9/0833Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP] involving conference or group key
    • H04L9/0836Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP] involving conference or group key using tree structure or hierarchical structure
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/16Analogue secrecy systems; Analogue subscription systems
    • H04N7/162Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
    • H04N7/163Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing by receiver means only
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00Television systems
    • H04N7/16Analogue secrecy systems; Analogue subscription systems
    • H04N7/167Systems rendering the television signal unintelligible and subsequently intelligible
    • H04N7/1675Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04HBROADCAST COMMUNICATION
    • H04H2201/00Aspects of broadcast communication
    • H04H2201/70Aspects of broadcast communication characterised in that receivers can be addressed

Abstract

Procedure for issuing and revoking the authorization to receive broadcasts protected by encryption with a decoder,
The keys of all the decoders concerned form a tree structure,
- where the nodes following the root and the individual nodes are assigned keys,
Wherein the leaves of this tree are assigned fixed keys which are uniquely associated with a decoder or part of a decoder (eg a chip card),
- Wherein the keys, each forming a branch of the tree structure, are stored in a respective decoder, and
The keys stored in a respective decoder serve to decrypt received cryptograms which cause changes to the stored keys and a stored system key,
- Wherein the root of the tree structure of the system key is assigned, which is used to decrypt a control word received with the respective broadcast and
- where those keys that are assigned to such nodes, which ...

Description

  • The The invention relates to a method for issuing and withdrawing the Authorization to receive broadcasts protected by encryption, with a decoder and one suitable for carrying out the method Decoder.
  • Paid Broadcasts, which also include the keywords pay-TV, pay-radio, become known are encrypted with a key CW. user are thereby authorized to receive that one gives them the key (control word) CW confidentially. This will be in general, the user a personal key PK to disposal usually physically secured against duplication, for example stored on a chip card.
  • The Control word CW is encrypted as a cryptogram ECM (Entitlement Control Message) over a Data channel of the radio station from the receiver or decoder received. By decryption this cryptogram by means of the personal key PK the control word CW is retrieved. When under the name EuroCrypt became known system becomes another cryptogram EMM (Entitlement Management Message) of a SK key sent. This cryptogram can be decrypted with the help of PK become. The key thus obtained SK is used to calculate CW from the cryptogram ECM. This access control system is described in DIN EN 50094. For safety's sake, the key is CW changed frequently.
  • A important task of the access control system is to provide users, not their fees have paid the permission to receive the broadcast to withdraw. This can on the one hand by a negative addressing happen at which a message is sent to the decoder, in which he is asked to cease his activity. These possibility is however basically unsure, as such news of a fraudulent Users can be intercepted and thus ineffective.
  • at the positive addressing will disable the decoder causes the information contained in it is made worthless. This happens in that all other decoders receive new information that will help decipher future ones It is absolutely necessary to use radio broadcasts, only the one to be switched off Decoder not.
  • The Although the method of positive addressing certainly leads to Disconnecting the decoder of each user, it is, however with big Expenses connected because to turn off a decoder messages must be sent to all other decoders.
  • By EP 0 641 103 A2 For example, a method and arrangement for key distribution in a selective broadcasting system having a plurality of subscribers has become known, wherein changeable groups of privileged subscribers are provided with keys and the keys are arranged in a tree structure. A withdrawal of the authorization to receive broadcasts is not provided.
  • Of the Invention is based on the object, a method for issuing and to propose the withdrawal of the right to receive broadcasts, where required for decryption Information in a particular decoder be made worthless can, without all other decoders must be addressed individually.
  • This object is achieved with the method according to the invention,
    • The keys of all the decoders concerned form a tree structure,
    • - where the nodes following the root and the individual nodes are assigned keys,
    • Wherein the leaves of this tree are assigned fixed keys which are uniquely associated with a decoder or part of a decoder (eg a chip card),
    • - Wherein the keys, each forming a branch of the tree structure, are stored in a respective decoder, and
    • The keys stored in a respective decoder serve to decrypt received cryptograms which cause changes to the stored keys and a stored system key,
    • - Wherein the root of the tree structure of the system key is assigned, which is used to decrypt a control word received with the respective broadcast and
    • - wherein the keys associated with such nodes immediately following a particular node serve to decrypt cryptograms containing a key to be reassigned to the particular node.
  • With 1,000,000 decoders 999,999 messages would have to be transmitted in the process mentioned above to deactivate one of the decoders four. In the method according to the invention with, for example, a 2-ary tree of depth 20, only about 40 messages are necessary.
  • to encoding the data can in the method according to the invention Both symmetric and asymmetric methods are used become.
  • An advantageous embodiment of the method according to the invention is that the tree structure is m-regular, where m t ≥ n with m = number of nodes following a node or root, t = number of levels formed by nodes, and n = number of decoders , As a result, a simple assignment of the cryptograms, which cause changes to the stored keys, possible.
  • For the withdrawal of the authorization of a particular decoder can be provided in the inventive method that
    • For each decoder other than the particular decoder which follows the same node together with the particular decoder, a cryptogram containing the key coded with the decoder's fixed key, which is reassigned to the common node, is sent;
    • Starting with the node preceding the common node, until the root for each subsequent node of all the node indirectly preceding the particular decoder, a cryptogram containing, respectively, the key encrypted with the key of the respective subsequent node is sent Decoder is indirectly remapped to the preceding node.
  • One advantageous decoder for carrying out the Method according to one of the preceding claims, characterized that several keys storable where at least part of the keys are received by the broadcasts Cryptograms that can be decrypted using one of the stored keys are, changeable are.
  • One embodiment the invention is illustrated in the drawing with reference to several figures and explained in more detail in the following description. It shows:
  • 1 a schematic representation of the tree-forming nodes, each associated with a key, the number of decoders is greatly reduced compared to reality, and
  • 2 a sequence of messages to be sent to revoke the authority of a particular decoder.
  • 1 shows as an example a 3-ary tree of depth 2 with keys associated with the node of the tree. The keys K (2, i) are permanently assigned to a decoder Di or a chip card. In the illustrated example, i = 1, ..., 9. The root of the tree is assigned the system key SK = K (0,1), while the m successor node of the node to which the key K (r, s) is assigned which are assigned keys K (r + 1, m s-1 + 1), ... K (r + 1, m s-1 + m).
  • A decoder with the key K (m, x) - while in 1 Example K (2, i) - the authorization to receive a pay-service broadcasting program may be granted by communicating valid keys on the way within the tree from K (m, x) to K (0,1). This requires a maximum of t-1 messages with the cryptograms of the next higher key. A decoder with the key K (m, x) can be deprived of the authorization to receive a paid radio program by replacing all keys on the way from K (m, x) to K (0,1). This requires a maximum of t · m messages with the cryptograms of the new keys. The keys that need to be exchanged to grant or revoke privilege can be easily calculated using a regular tree structure.
  • 2 shows a sequence of messages to decoder D9 using the in 1 to disable the described tree structure of the keys. Each message can be broadcast over a broadcast channel. It has an address and a payload in 2 separated by a vertical bar. With the help of the address, each decoder recognizes whether it has to process a specific received message. The payload contains a cryptogram that can only be evaluated by the addressed decoders. The notation A <B> means that the information B was encrypted with the key A. The algorithm for decryption is known in the decoder.
  • Line a the 2 shows a message to the decoder D7, with which this new K gets a new key (1,3). The decoder D8 also receives the same new key, but in this case it is decrypted via the key K (2,8) (line b). In the message according to line c, an address is given, which is common to the decoders D1 to D3 and in 2 is designated group 1. These have in common the key K (1,1), which is used to decrypt the new system key SKneu. In the same way then for the group 2 (decoder D4 to D6) and for the group 3 (decoder D7 to D9), the new system key SKnew transmitted (lines d and e). However, the decoder D9 is not able to decrypt the cryptogram K (1,3) new <SKnew>. The decoder D9 thus receives no new system key SKnew and can no longer decode the subsequently transmitted useful signals.

Claims (4)

  1. Procedure for issuing and revoking the authorization for receiving broadcasts by encryption protected are, with a decoder, - in which the keys all affected decoders form a tree structure, - in which the key assigned to the root and the individual nodes are, - in which the leaves This tree is assigned fixed keys are clearly a decoder or part of a decoder (e.g., a smart card), - where the keys, the each forming a branch of the tree structure, each in a decoder be saved and - in which the decryption key stored in each decoder serve received cryptograms, which changes the stored key and a stored system key, - in which the root of the tree is assigned to the system key used for decryption a control word received with the respective broadcast serves and - in which those keys, which are assigned to such nodes, which a specific node immediately succeed, to decrypt cryptograms that a key which is to be reassigned to the particular node.
  2. Method according to claim 1, characterized in that the tree structure is m-regular, where m t ≥n with m = number of nodes following a node or root, t = number of levels formed by nodes, and n = number of decoders.
  3. Method according to one of claims 1 or 2, characterized that to Withdrawal of the authorization of a particular decoder - for each Decoder except the particular decoder, along with the particular decoder Following the same node, a cryptogram is sent, which is the with the firm key encrypted by the decoder key contains which is reassigned to the common node, - starting with the node preceding the common node to the root for each all subsequent nodes of all the particular decoder indirectly each node is sent a cryptogram, the the one with the key contains the encrypted key of each successive node, the reassigned to the node indirectly preceding the particular decoder becomes.
  4. Decoder for performing the method according to a of the preceding claims, characterized in that a plurality Key storable are at least part of the keys through with the broadcasts received cryptograms that can be decrypted using one of the stored keys are, changeable are.
DE1995111298 1995-03-28 1995-03-28 Procedure for issuing and revoking the authorization to receive broadcasts and decoders Expired - Lifetime DE19511298B4 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE1995111298 DE19511298B4 (en) 1995-03-28 1995-03-28 Procedure for issuing and revoking the authorization to receive broadcasts and decoders

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1995111298 DE19511298B4 (en) 1995-03-28 1995-03-28 Procedure for issuing and revoking the authorization to receive broadcasts and decoders

Publications (2)

Publication Number Publication Date
DE19511298A1 DE19511298A1 (en) 1996-10-02
DE19511298B4 true DE19511298B4 (en) 2005-08-18

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DE19630707A1 (en) * 1996-07-30 1998-02-05 Deutsche Telekom Ag Methods and arrangements for avoiding Unauthorized use of distribution networks
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US7587044B2 (en) 1998-01-02 2009-09-08 Cryptography Research, Inc. Differential power analysis method and apparatus
DE69834431T3 (en) 1998-01-02 2009-09-10 Cryptography Research Inc., San Francisco Liquid resistant cryptographic process and device
WO1999067919A2 (en) 1998-06-03 1999-12-29 Cryptography Research, Inc. Improved des and other cryptographic processes with leak minimization for smartcards and other cryptosystems
DE69935913T2 (en) 1998-07-02 2008-01-10 Cryptography Research Inc., San Francisco Lack resistant upgrade of an indexed cryptographic key
EP0987893A1 (en) * 1998-09-16 2000-03-22 CANAL+ Société Anonyme Management of data in a receiver/decoder
DE19847941A1 (en) 1998-10-09 2000-04-13 Deutsche Telekom Ag Common cryptographic key establishment method for subscribers involves successively combining two known secret values into a new common value throughout using Diffie-Hellmann technique
EP1075108A1 (en) 1999-07-23 2001-02-07 BRITISH TELECOMMUNICATIONS public limited company Cryptographic data distribution
JP2001352321A (en) * 2000-04-06 2001-12-21 Sony Corp Information processing system, information processing method, and information recording medium, and program providing medium
JP4023083B2 (en) * 2000-04-06 2007-12-19 ソニー株式会社 Information processing system, information processing method, information recording medium, and program providing medium
JP4370721B2 (en) * 2000-04-06 2009-11-25 ソニー株式会社 Information recording apparatus, information reproducing apparatus, information recording method, information reproducing method, key update terminal apparatus, generation management key update method, information recording medium, and program providing medium
JP4622064B2 (en) 2000-04-06 2011-02-02 ソニー株式会社 Information recording apparatus, information reproducing apparatus, information recording method, information reproducing method, information recording medium, and program providing medium
AU779440B2 (en) 2000-06-21 2005-01-27 Sony Corporation Information recording/reproducing apparatus and method
DE60137085D1 (en) 2000-06-21 2009-01-29 Sony Corp Device and method for key renewal in a hierarchical tree key structure
JP4608749B2 (en) 2000-07-24 2011-01-12 ソニー株式会社 Data processing apparatus, data processing method, license system, and program providing medium
JP4660899B2 (en) * 2000-07-24 2011-03-30 ソニー株式会社 Data processing apparatus, data processing method, and program providing medium
DE10038068A1 (en) * 2000-08-04 2002-02-14 Deutsche Telekom Ag A method for transmitting data
US20020076204A1 (en) * 2000-12-18 2002-06-20 Toshihisa Nakano Key management device/method/program, recording medium, reproducing device/method, recording device, and computer-readable, second recording medium storing the key management program for copyright protection
JP2002319932A (en) 2001-04-19 2002-10-31 Sony Corp Device and method for recording information, device and method for reproducing information, and program
WO2003107588A1 (en) * 2002-06-17 2003-12-24 Koninklijke Philips Electronics N.V. System for authentication between devices using group certificates
EP1575292A1 (en) 2004-03-10 2005-09-14 Nagracard S.A. Method of securing a scrambled content sent by a broadcaster
DE102004042094B3 (en) * 2004-08-30 2005-09-22 RUHR-UNIVERSITäT BOCHUM Digital data transmission method such as for pay TV using a single use code
WO2007059807A1 (en) * 2005-11-22 2007-05-31 Nero Ag Apparatus and method for retrieving a decryption key, license server and media player
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