Patents by Inventor Silvio Micali

Silvio Micali has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5666416
    Abstract: A method of managing certificates in a communication system having a certifying authority and a directory. Preferably, the method begins by having the certifying authority generate certificates by digitally signing a given piece of data. At a later point time, the certifying authority may produce a string that proves whether a particular certificate is currently valid without also proving the validity of at least some other certificates. The technique obviates use of certification revocation lists communicated between the certifying authority and the directory.
    Type: Grant
    Filed: November 16, 1995
    Date of Patent: September 9, 1997
    Inventor: Silvio Micali
  • Patent number: 5666414
    Abstract: A given decryption key is decomposed into at least two parts, for example, a first subkey and a second subkey. The first subkey may be verifiably secret-shared among a set of one or more trustees, whereas the trustees preferably receive no information at all about the second subkey. Reconstruction of the first subkey by the trustees does not yield a decryption key useful by itself in decrypting ciphertexts. The trustees, however, also receive a guarantee that once they reveal their shares to a given entity, the entity has the capability of determining the second subkey. Generally, the generation of the second subkey will be carried out by the entity using a brute force technique, although the calculation may be performed by still another party (or even the trustees themselves in cooperation with the entity). Once the second subkey is determined, the guarantee ensures that combination of the first and second subkeys yields a given decryption key that may then be used to decrypt ciphertexts.
    Type: Grant
    Filed: March 21, 1996
    Date of Patent: September 9, 1997
    Inventor: Silvio Micali
  • Patent number: 5666420
    Abstract: A communication method between a first and second party, in the presence of a trusted party, that enables a transaction in which the second party receives a first value produced by the first party and unpredictable to the second party if and only if the first party receives a second value produced by the second party and unpredictable to the first party. The method includes two basic steps: exchanging a first set of communications between the first and second parties without participation of the trusted party to attempt completion of the transaction, and if the transaction is not completed using the first set of communications between the first and second parties, having the trusted party take action to complete the transaction.
    Type: Grant
    Filed: November 18, 1996
    Date of Patent: September 9, 1997
    Inventor: Silvio Micali
  • Patent number: 5638447
    Abstract: Digitally signing data includes collecting a group of signers, each having a public key and a corresponding secret key, a subgroup of signers each producing a partial digital signature of the data, and obtaining a combined signature of the data by combining the partial digital signatures of the data, where the combined digital signature keeps the subgroup of signers accountable for the data for which the subgroup of signers each produce a partial digital signature. Verifying a digital signature of data includes ascertaining members of a subgroup of signers that contributed to provide the digital signature of the data, determining a combined public key corresponding to individual secret keys of a the subgroup of signers, and using the combined public key to verify that the subgroup of signers have each contributed to provide the digital signature of the data.
    Type: Grant
    Filed: May 15, 1996
    Date of Patent: June 10, 1997
    Inventor: Silvio Micali
  • Patent number: 5629982
    Abstract: A number of electronic communications methods are described involving a first and a second party (i.e., sender and recipient), with assistance from at least a trusted party, enabling electronic transactions in which the first party has a message for the second party. The first party, the second party and the trusted party undertake an exchange of transmissions, such that if all transmissions reach their destinations the second party only receives the message if the first party receives at least one receipt. Preferably, the identity of the first party is temporarily withheld from the second party during the transaction. At least one receipt received to the first party enables the first party to prove the content of the message received by the second party.
    Type: Grant
    Filed: August 20, 1996
    Date of Patent: May 13, 1997
    Inventor: Silvio Micali
  • Patent number: 5615269
    Abstract: There is described an electronic communications method between a first party and a second party, with assistance from at least a plurality of trustees, enabling an electronic transaction in which the first party having a selling reservation price (SRP) and the second party having a buying reservation price (BRP) may be committed to a transaction if a predetermined relationship between SRP and BRP is established, but not otherwise. The method begins by having each of the parties transmit shares of their respective reserve prices to the trustees. These shares are such that less than a given number of them does not provide enough useful information for reconstructing the reserve prices while a sufficiently high number of them allows such reconstruction. The trustees then take some action to determine whether the predetermined relationship exists without reconstructing SRP and BRP.
    Type: Grant
    Filed: February 22, 1996
    Date of Patent: March 25, 1997
    Inventor: Silvio Micali
  • Patent number: 5610982
    Abstract: Certifying data includes having a subgroup of authorities each contribute a partial digital signature of the data to enable computation of a combined signature where the subgroup includes some, but not all, of the total number of authorities capable of applying a partial signature to the data, issuing a certificate for the data, and storing information in order to keep the subgroup of authorities accountable for the data that the subgroup of authorities contribute to eerily. In another scheme, certifying data can include having one or more lower-level authorities cause top-level authorities to receive an indication that the data is to be certified. A first subgroup of top-level authorities each applies a partial digital signature to the data. A certificate is issued containing a combined digital signature of a second subgroup of top-level authorities.
    Type: Grant
    Filed: May 15, 1996
    Date of Patent: March 11, 1997
    Inventor: Silvio Micali
  • Patent number: 5604804
    Abstract: A method for certifying public keys of a digital signature scheme in a communications system is provided. The secure communications system is one in which there are at least two levels of authorities. A user presents a piece of data to an intermediate level authority who, upon verifying the data, causes an issuing authority to issue a certificate that the piece of data posses a given property. Although the certificate is compacted by not having it contain a pubic key of the intermediate authority, nonetheless, information is stored in order to keep the intermediate authority accountable.
    Type: Grant
    Filed: April 23, 1996
    Date of Patent: February 18, 1997
    Inventor: Silvio Micali
  • Patent number: 5537475
    Abstract: A digital signature scheme wherein the signature of a message M relative to a public key is computed by means of a secret key. The scheme begins by having the user select a number x independent of M. This step may occur off-line and before there is any knowledge of the particular message M to be signed. To sign the message, the routine computes a description of a function G which is dependent of the message M, and then applies the function G to x to produce a string z. The routine outputs z and a description of a second function F as the desired signature of the message M. Thus according to the invention a signature of the message is obtained by applying to an independent argument x a function dependent on M. This operation provides enhanced efficiency and security over the prior art and facilitates use of the scheme to allow multiple users of a secure communications system to share the same public key; alternatively, the scheme is useful for generating short certificates of public keys used in such systems.
    Type: Grant
    Filed: February 1, 1994
    Date of Patent: July 16, 1996
    Inventor: Silvio Micali
  • Patent number: 5519778
    Abstract: The present invention describes a method for enabling users of a cryptosystem to agree on secret keys. In one embodiment, a trusted agent chooses at least one individual key for each user, with at least a portion of such individual key being secret. At least some of the individual keys are then stored in physically secure devices, and the pair of users i and j use their individual keys to compute a common secret key. In another embodiment, each trustee of a group of trustees choose at least one individual key for each user, with at least some portion of such individual key being secret. The keys chosen by a sufficiently small number of such trustees, however, are insufficient for computing the common secret key of the users. Other hardware and software key exchange protocols based on these two techniques are also disclosed.
    Type: Grant
    Filed: September 26, 1994
    Date of Patent: May 21, 1996
    Assignee: Silvio Micali
    Inventors: Frank T. Leighton, Silvio Micali
  • Patent number: 5499296
    Abstract: Secure devices (e.g., a cryptophone, a cryptofax, a computer or other such electronic device) have an encryptor and a digitizer, the digitizer for receiving an input and generating an output supplied to the encryptor. According to the invention, the encryptor and the digitizer are coupled either physically, logically or through non-tamperable software to guarantee that a given ciphertext is the encryption, generated by the encryptor, of an output generated by the digitizer.
    Type: Grant
    Filed: August 22, 1994
    Date of Patent: March 12, 1996
    Inventor: Silvio Micali
  • Patent number: 5432852
    Abstract: The present invention describes new digital signature schemes that are provably secure against any adaptive chosen-message attack. The scheme, which is based on selection of a hash function from a space of such functions, has a very short public key, fast signing, a reasonable signature length and high security. Several algorithmic techniques are provided for enhancing the efficiency of the signature scheme in terms of time and memory.
    Type: Grant
    Filed: September 29, 1993
    Date of Patent: July 11, 1995
    Inventors: Frank T. Leighton, Silvio Micali
  • Patent number: 5420927
    Abstract: A method for certifying public keys of a digital signature scheme in a secure communications system is provided. The secure communications system in one in which there are authorities with previously-certified public verification keys. The method begins by having a user U present an authority a verification key PK.sub.U. The authority then identifies the presenting user as U. Thereafter, the authority verifies that the presenting user knows the secret signing key associated with PK.sub.U. If so, the authority computes a digital signature S relative to the authority's own public key PK.sub.A of its verification that PK.sub.U is the public key of user U. The authority then issues a certificate that PK.sub.U is the public key of user U, the certificate including both S and a certificate for PK.sub.A.
    Type: Grant
    Filed: February 1, 1994
    Date of Patent: May 30, 1995
    Inventor: Silvio Micali
  • Patent number: 5351302
    Abstract: The method and system of the present invention utilizes public-key cryptography to create "secure" titles for personal and real property such as vehicles and the like. The title preferably comprises a card in which is stored a digital signature of one or more identifiers such as a vehicle identification number, the vehicle license plate and the owner's name. To effect a transfer of the property, the digital signature on the title must first be shown to have been generated from the one or more identifiers.
    Type: Grant
    Filed: May 26, 1993
    Date of Patent: September 27, 1994
    Inventors: Frank T. Leighton, Silvio Micali
  • Patent number: 5315658
    Abstract: A method, using a public-key cryptosystem, for enabling a predetermined entity to monitor communications of users suspected of unlawful activities while protecting the privacy of law-abiding users, wherein each user is assigned a pair of matching secret and public keys. According to the method, each user's secret key is broken into shares. Then, each user provides a plurality of "trustees" pieces of information. The pieces of information provided to each trustee enable that trustee to verify that such information includes a "share" of a secret key of some given public key. Each trustee can verify that the pieces of information provided include a share of the secret key without interaction with any other trustee or by sending messages to the user. Upon a predetermined request or condition, e.g., a court order authorizing the entity to monitor the communications of a user suspected of unlawful activity, the trustees reveal to the entity the shares of the secret key of such user.
    Type: Grant
    Filed: April 19, 1993
    Date of Patent: May 24, 1994
    Inventor: Silvio Micali
  • Patent number: 5276737
    Abstract: A method, using a public-key cryptosystem, for enabling a predetermined entity to monitor communications of users suspected of unlawful activities while protecting the privacy of law-abiding users, wherein each user is assigned a pair of matching secret and public keys. According to the method, each user's secret key is broken into shares. Then, each user provides a plurality of "trustees" pieces of information. The pieces of information provided to each trustee enable that trustee to verify that such information includes a "share" of a secret key of some given public key. Each trustee can verify that the pieces of information provided include a share of the secret key without interaction with any other trustee or by sending messages to the user. Upon a predetermined request or condition, e.g., a court order authorizing the entity to monitor the communications of a user suspected of unlawful activity, the trustees reveal to the entity the shares of the secret key of such user.
    Type: Grant
    Filed: April 20, 1992
    Date of Patent: January 4, 1994
    Inventor: Silvio Micali
  • Patent number: 5016274
    Abstract: A method for "on-line/off-line" digital signing is described and begins by pre-computing a data string x from a pair of matching public and secret keys of a digital signature scheme such that, for any message m later selected to be signed, a signature of m derived from x can be computed substantially faster than the signature of m derived from the matching public and secret keys. After a message m is selected to be signed, the method computes a signature .sigma. of the message m using the data string x. Because the method uses a two-stage approach to sign a message, the technique can be advantageously used to enhance the security of known digital signature schemes or to effect transaction processing using "smart" cards.
    Type: Grant
    Filed: November 8, 1988
    Date of Patent: May 14, 1991
    Inventors: Silvio Micali, Oded Goldreich, Shimon Even
  • Patent number: 4995081
    Abstract: The method and system for the invention utilizes any of a number of "proofs of legitimacy" to generate and verify a personal identification card. A card is generated by computing a digital signature of a non-secret password. The password and the digital signature are then encoded and stored on a magnetic stripe or other memory device of the card. To effect a transaction, the digital signature on a received card must be shown to have been generated from the password on the received card. The password preferably includes a digitized photograph of the authorized cardholder which is capable of being displayed at the transaction terminal. This enables the operator of the terminal to verify the identity of the cardholder by visual inspection.
    Type: Grant
    Filed: November 6, 1989
    Date of Patent: February 19, 1991
    Inventors: Frank T. Leighton, Silvio Micali
  • Patent number: 4944009
    Abstract: A seed random sequence is extended in successive nodes of a tree structure of a random sequence generator. At each node, an input sequence is expanded to an output sequence substantially greater than the length of the input sequence. Plural processors operate in parallel in generating the final output sequence, and subsequences may be directly accessed as a starting location of the output sequence. The random sequence generator is accessed by an index in an encryption system. In a sequential generator, less than all of the bits from the generator unit are reapplied to the generator unit in an iterative process.
    Type: Grant
    Filed: February 25, 1988
    Date of Patent: July 24, 1990
    Assignee: Massachusetts Institute of Technology
    Inventors: Silvio Micali, Claus Schnorr
  • Patent number: 4879747
    Abstract: The method and system of the invention utilizes a private key of a public-key cryptosystem key pair to encrypt a non-secret password into a digital signature. The password and the digital signature are then encoded and stored on a magnetic stripe or other memory device of the card. To effect a transaction, the digital signature on a received card must be shown to have been generated from the password on the received card. The password preferably includes a digitized photograph of the authorized cardholder which is capable of being displayed at the transaction terminal. This enables the operator of the terminal to verify the identity of the cardholder by visual inspection.
    Type: Grant
    Filed: March 21, 1988
    Date of Patent: November 7, 1989
    Inventors: Frank T. Leighton, Silvio Micali