Digital Equipment Corporation

Joseph J Tardo

Charles W Kaufman

Butler W Lampson

Morrie Gasser

William R Hawe

Amar Gupta

Kannan Alagappan

Barry A Spinney

Gregory M Waters

Mark F Kempf

B J Herbison

Apparatus for protecting the confidentiality of a user's password during a remote login authentication exchange between a user node and a directory service node of a distributed, public key cryptography system includes a specialized server application functioning as an intermediary agent for the login procedure. The login agent has responsibility for approving the user's login attempt and distributing a private key to the user. However, the login agent is not trusted with the user's password and is therefore a 'semi-trusted' node. In another aspect of the invention, a login protocol enables remote authentication of the user password without transmitting the password over the network.

Method and apparatus for protecting the confidentiality of passwords in

A decryption method, and associated cryptographic processor, for performing in-line decryption of information frames received from a communication network through a first in-line processing stage. As an information packet is streamed into the cryptographic processor, a determination is made to an acceptable level of probability whether the packet contains data that should be decrypted. The decision whether or not decrypt is made by analyzing the incoming packet header, recognizing a limited number of packet formats, and further parsing the packet to locate any encrypted data and to make sure that the packet is not a segment of a larger message. Falsely decrypted packets are looped back through the cryptographic processor, to regenerate the data that was falsely decrypted. Decryption and encryption are performed in such a manner that a false decryption is completely reversible without loss of data. Special treatment is provided for packets containing data that cannot be divided into an integral number of standard blocks required for decryption processing.

Probabilistic cryptographic processing method

A method and related cryptographic processing apparatus for handling information packets that are to be cryptographically processed prior to transmission onto a communication network, or that are to be locally cryptographically processed and looped back to a node processor. A special cryptographic preamble is included in each information packet that is to be subject to cryptographic processing. The cryptographic preamble contains an offset value pointing to the starting location of information that is to be processed, and completely defines the type of cryptographic processing to be performed. The cryptographic processor can then perform the processing as specified in the preamble without regard to a specific protocol. If the packet is to be transmitted onto the network, the preamble is stripped from the packet after cryptographic processing, so that the formats of packets transmitted onto the network will be unaffected by the preamble. Cryptographic processing modes include encryption of data for outbound transmission, encryption of a cipher key for loopback to the node processor, encryption or decryption of data for loopback to the node processor, and computation of an integrity check value for loopback to the node processor.

Generic encryption technique for communication networks

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Acton, MA, United States of America

Joseph J Tardo