Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
  • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
  • H04L9/0819—Key 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)
  • H04L9/083—Key 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]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
  • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
  • H04L9/0819—Key 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)
  • H04L9/0822—Key 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) using key encryption key
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
  • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
  • H04L9/0819—Key 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)
  • H04L9/0825—Key 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) using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
  • H04L2209/04—Masking or blinding

Definitions

• the present invention relates to an instrument for securing messages, each message having a sender, a receiver and a content, the securing consisting in implementing means making it possible to associate with the message, when it is sent, an encrypted indication guaranteeing the authentic character of the message with regard to certain sensitive parameters of the latter and of the identities of its sender and of its recipient and of verifying or checking this encrypted indication on reception of the message by means of decryption which are in relation to the encryption means which were used to develop the numerical indication.
• the encrypted indication may accompany the content of the message which is readable “in clear”; this indication will then be called a seal and the encryption which will be discussed below will be called seal. In other cases, it is the content itself of the message which is encrypted and the encryption is then called encryption, the information contained not being readable in clear.
• the sealing or encryption are known and implement an encryption algorithm for one or more sensitive data of the message, or even of the entire message, by means of an encryption key which is personal to the sender.
• the control of the seal or the decryption is carried out with an appropriate algorithm and a key which can be different from the encryption key (in which case the algorithm is asymmetric) or which can be the same (the algorithm then being symmetrical).
• the invention therefore relates to a security instrument for the encryption / decryption of messages exchanged between each of the actors of a network of a plurality of actors who can act as sender or recipient of an encrypted or sealed message which comprises, for each actor, a device comprising an integrated circuit with memory zones and a microprocessor capable of executing an algorithm and of controlling access to these zones according to the nature of the operation requested from the microprocessor by the operator who owns the device and chosen from among the operations:
• the first advantage of the instrument of the invention results from this technological specificity (namely the values of hidden base keys and their selective access by the microprocessor according to the operation which is assigned to it).
• This arrangement allows the implementation by each microprocessor of symmetrical algorithms, therefore fast, while having created a global system of encryption / decryption (sealing / control or encryption / decryption) asymmetrical, therefore very important security.
• the messages to be processed are messages sent by a transmitter to receivers.
• a certain security is usually ensured as to the authenticity of the transmission of the message by practicing the sealing technique.
• the sender encodes certain data characteristic of his message by a cryptographic algorithm using a key of his own. The result of this operation is called the seal.
• the message receiver (or controller) checks the seal using the same key applied to the same data they know. With the means of the invention, the sender and the recipients will proceed to seal one and the others to verify the seal in a completely conventional manner.
• the transmitter has the device (integrated circuit card for example) of the invention, in which a microprocessor has two operating modes: a first mode called “public key calculation” (key to communicate) and a second so-called “seal calculation” mode.
• This integrated circuit also includes memory areas which contain two addresses at each of which is housed a masked value (known as the basic key) unknown not only to the wearer of the device but also to the manufacturer. These addresses are only accessible by the microprocessor during the execution of the functions to be executed.
• first basic key T is accessible by the microprocessor only during the execution of the "seal calculation" function which is an encryption function
• the other value (second key U) being accessible only during the execution of the "public key calculation” function which implements a decryption algorithm.
• the actors receiving or receiving the sealed message also have the same device (integrated circuit card) with a microprocessor and memory areas. In a version of the invention simplified for the purposes of the explanation, these memory areas contain at an address, access controlled by the microprocessor, a value identical to the second base key U introduced in the card of the transmitter and the microprocessor only has a "seal verification" function which is a decryption function.
• the second basic key is of course unknown to the card holder and to its manufacturer.
• the sender in a conventional manner, must above all communicate to the receivers a key allowing the latter to verify the seals that he has affixed to his messages. To do this, he chooses a key of arbitrary value S which is specific to him and which becomes his signature. It provides this signature to the device of the invention in its "public key calculation" mode.
• the function executed by the microprocessor then consists in encrypting this key S by an algorithm A by means of the first basic key T and in encrypting again the result obtained by the inverse algorithm l / A of the algorithm A by means of the second base key U.
• the value obtained constitutes the public key V, the key to be communicated to each of the receivers. It is possible to write synthetically:
• V [S (A) T] (1 / A) U, with (A) T meaning encryption of the key S by the algorithm A using the key T and (l / A) U meaning encryption by the inverse of algorithm A using the key U (which is a decryption operation).
• the key V thus calculated is transmitted to the receivers.
• the transmitter to seal its message selects the "seal calculation" function of the microprocessor. he introduces at the input of the device the message M to be sealed and the signature key S chosen.
• the microprocessor proceeds to the encryption of the key S by the algorithm A by means of the first basic key T to obtain the sealing key K.
• K S (A) T which is not accessible for the sender and with which it calculates the seal associated with the message S (noted below Se (M / S)).
• the receiver has the device of the invention in which the microprocessor has a "seal verification" operating mode and a memory area accessible only by the microprocessor during the execution of this function, loaded with the same value U than the second basic key of the transmitter device.
• the receiver having the key V receives the message (in clear) and proceeds to verify the seal associated with this message by selecting the "seal verification" function which is a decryption function executable by the microprocessor of the device which it holds. This decryption is carried out by means of the key K which is calculated by the microprocessor during the execution of the verification of the seal and this for each verification operation, without possible access for the receiver. So the microprocessor, to have the key
• K proceeds to the encryption of the key V by means of the second basic key U by the algorithm A.
• U (A ) U S (A) T
• the microprocessor of the receiver performs with this key the calculation of the seal and delivers to the receiver the result of the comparison the value of the seal which it has just calculated with that which it received from the transmitter .
• the basic commands illustrate the degree of security obtained in the transaction between a transmitter and a receiver, thanks to the two hidden keys T and U which are only accessible by the microprocessor and this selectively according to the function executed by this microprocessor.
• the masking and this selective accessibility are carried out at the very stage of the manufacture of the memory card and of the integrated circuit so that it is not possible to access it by means of any fraudulent operation by application of software for example .
• the device of the invention provides the exchange with the same security as an asymmetric encryption algorithm with the advantages of a symmetric algorithm.
• FIG. 1 is a diagram of a basic device of the invention
• FIGS. 1A, 1B and 1C illustrate the steps already described relating to the sealing of a message and the verification of a seal
• FIG. 2 illustrates an alternative embodiment of this device allowing the selectivity of exchanges between the actors of a network, the strengthening of the authentication of a message, the encryption / decryption, the intervention of a trusted third party , an official depository of the keys ...
• FIG. 3 illustrates an alternative embodiment of the device allowing the reinforcement of the verification
• FIG. 4 illustrates another example of use of the instrument according to the invention.
• the device represented in FIG. 1 is a memory card E ⁇ ⁇ with integrated circuits which comprises a microprocessor 1, a first memory address 2 containing a basic key T- . of a first type, that is to say called by the microprocessor during the execution of an encryption function, a second memory address 3 containing a base key U of a second type, i.e. - say called by the microprocessor when it executes a decryption operation, an input 4 to receive the data to be processed and an output 5 to deliver the processed data.
• the device also includes control means 6 to 10 for selecting the operating mode of the microprocessor from the following five operating modes:
• the operating modes "seal calculation” and “encryption” are encryption functions which use only the hidden keys of the first type T.
• the operating modes “seal verification” and “decryption” are decryption functions which use only call to the hidden keys U of the second type.
• the "public key calculation” operating mode is an encryption function followed by a decryption function successively using two types of keys.
• This memory card is made available to all the actors of a message exchange network, each actor being able to be in this network either sender of the message or receiver or recipient of the message sent.
• the only difference from one card to another is the value of the basic key of the first type which is different T x T 2 etc. from one card to another.
• This device allows the message to be either sealed or encrypted, the basic functionalities that it includes allowing, as will be explained below, to meet the legal requirements attached to encryption / decryption.
• FIG. 1A schematically illustrates the calculation of the public key V by the holder of the card E x which is intended for the holder of the card E 2 of FIG. 1C, identical to the card E 1 except as regards the basic key of the first type, that is to say that used by the microprocessor when in its operating mode it proceeds to an encryption operation.
• This basic key is denoted T 2 in FIG. 1C.
• FIG. 1B illustrates the sealing (calculation of a seal) of a message M as described above.
• FIG. 1C illustrates the verification of a seal by the holder of the card E 2 which, acting as a receiver, uses the operating mode 9 of the microprocessor 1, applied to the information received from the holder of the card E 1 # it ie the message M, the seal Se (M / S), the public key V, data placed at the input of the microprocessor 1, the latter delivering validation information O or rejection N after the verification processing described above.
• the value of the basic key U used for a decryption operation during the verification of the seal (or during the calculation of the public key) is common, each actor can develop a public key of its own and usable in decryption by all the other actors.
• FIG. 2 illustrates an alternative embodiment of the device of the invention by which it is possible to identify the sender of a sealed message and / or of a public key.
• the card represented includes all the functionalities of the previous card with in addition a memory area 11 at the address of which is housed a value I x which is an identification key of the card holder E ⁇ ⁇ . This value is introduced into the card at the time of its manufacture but can be extracted from it by the microprocessor to transmit it in clear. It is therefore not a hidden key like those T and U described above.
• the function for calculating the seal by a transmitter takes this key I x into account by concatenating it with the message M.
• the data transmitted to the receivers then includes the message M, the identification key l lt the seal Sc (MI 1 / S ) calculated and the public key V.
• the verification of the seal by the recipient who knows the sender by knowing the key I x which is transmitted to it, is carried out as already described by recalculating the seal from the message, from the key I 1 ( of a concatenation of these message and key by means of the key K calculated from the public key V and the masked basic key U.
• the fact that the key I x is imposed in the calculation by the microprocessor , without the possibility of external intervention, prohibits any risk of identity theft.
• each card comprises two basic keys Ul, U2 masked of the second type common to all the cards of the actors of the network.
• the number of basic keys can be multiplied by more than two.
• the interest of these two basic keys lies in the fact that the calculation of the public key and the verification function of the seal require to multiply the application of the cryptographic algorithm, which greatly complicates the cryptographic analysis which would be attempted to discover the key K.
• one of the two (or more) basic keys U of the second type is not frozen at the start, but obtained by calculation based on the identification keys assigned to each card.
• two actors of a network can communicate their identification key (a directory of network identification keys can be established).
• the public key of the issuing actor is calculated as described above, one of the algorithms implemented using one of the U type keys obtained dynamically from the two identification keys of the actors involved (the issuer key being present in a memory of the card, the recipient's key being presented as input at the same time as the signature key S).
• the public key then becomes usable only by the specified recipient to whom, with the message and the associated seal, the sender provides his identification key.
• the recipient's microprocessor can then re-establish the dynamic key U by recombining the identification key of the transmitter and its own internal identification key during the verification of the seal.
• each actor can communicate with all the others by providing them with a common public key or with only one of the others by using their identification key and that of the recipient chosen to develop a recipient public key.
• the cards can also include other identification keys in connection with the constitution of sub-assemblies of the network, these keys would be common to the members of the network satisfying such or such founding criterion of the sub-assembly in question.
• Each issuer could then manufacture a selective public key by subset.
• All the players in this field will have an instrument E (for example a memory card and microprocessor) with, as in FIG. 2, a basic key of the first type T1, a first memory area 11 at the address of which is stored the value I 1 forming the identification key of the card holder, a second memory area 12 at the address of which is housed a value D of domain identification and a basic key of the second type U D q ⁇ i is common to all cards in domain D.
• an instrument E for example a memory card and microprocessor
• the sender of the message uses his instrument to develop a seal Se which consists in encrypting by the key K a message which includes the message M itself (for example in clear), the identifiers transmitter receiver I 1 # IN 2 , the identification value of domain D, the unknown value U D (basic key of the second type) as well as the communication key V.
• a seal Se which consists in encrypting by the key K a message which includes the message M itself (for example in clear), the identifiers transmitter receiver I 1 # IN 2 , the identification value of domain D, the unknown value U D (basic key of the second type) as well as the communication key V.
• U D basic key of the second type
• the recipient On receipt of such a message accompanied by his signature, the recipient proceeds to verify the seal which he can achieve with the V key if he belongs to the same domain as the sender.
• the recipient can only have access to the decryption after having verified the seal. If this verification does not occur after a determined number of attempts, the decryption function is deactivated and the recipient will be unable to obtain the message M 'in clear.
• a message as structured as illustrated in FIG. 4 can constitute the part M or M ′ of a second message that, for example, the recipient will transmit to a second recipient.
• This second recipient if the first message is encrypted, will not be able to decrypt it because the decryption can only be carried out by the sender or the first recipient. He can however verify the seal.
• any message is, in this use case, sealed and therefore digitally signed. It therefore constitutes proof that can be included, encapsulated in another message.
• the device of the invention therefore makes it possible to adjust the security (confidentiality, signature, etc.) of the exchanges of computer data in a network, whether the exchange is of the private type (from a sender to a recipient) or public (a sender towards all the actors of the network or certain groups of them). It also makes it possible to fully decentralize the security procedures in a given network. Finally, it lends itself to encryption / decryption operations since it makes it possible to satisfy the public order requirements linked to this type of exchange.
• the invention makes it possible, in a network considered, to designate an administrator (a trusted third party) who, with the same means as those of each actor, can ensure, for example, the key management function, the guarding of these and their accessibility by the public authorities in the case of encryption.
• the sealing of a public key by the administrator may constitute a certificate of deposit thereof and proof of the completion of a formality in accordance with the legislation in force with regard to encrypted messages.
• the “encryption” operating mode of the device according to the invention can force the presentation to the microprocessor which will be technologically designed for this purpose, not only the encryption key of the holder (his signature) of the device but also the certificate of deposit of the corresponding public key that he will have obtained from a trusted third party.
• the microprocessor in the presence of this seal and at the call of an "encryption" operating mode could for example carry out a verification of the seal which, if it proves positive, will generate an authorization for execution by the microprocessor of the encryption procedure proper.

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• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Storage Device Security (AREA)
• Financial Or Insurance-Related Operations Such As Payment And Settlement (AREA)

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• 1997
  • 1997-09-01 US US09/254,270 patent/US6493823B1/en not_active Expired - Fee Related
  • 1997-09-01 EP EP97938966A patent/EP0923829A2/de not_active Withdrawn
  • 1997-09-01 WO PCT/FR1997/001542 patent/WO1998010563A2/fr not_active Ceased

Non-Patent Citations (1)

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