Patent ID: 6891952

Claim:
A method for generating and securely exchanging a key between a transmitter and a receiver, comprising the steps of: a) securely storing identical sets of random values in a transmitter buffer associated with the transmitter and in a receiver buffer associated with the receiver so that identical values with identical positions exist in each buffer, each of said buffers having a defined logical buffer size; b) displacing the random values stored in the transmitter buffer by a defined amount so that a random value at one end of the buffer drops out of the buffer and a position at the other end of the buffer becomes free; c) generating a new random value representing a portion of the key; d) storing the new random value in the position in the transmitter buffer that has become free; e) combining the new random value with the random value that has dropped out of the transmitter buffer to produce a first result; f) transmitting the first result to the receiver; g) combining the first result with the value in the receiver buffer that corresponds in position to the value in the transmitter buffer that has dropped out due to displacement to produce a second result; h) displacing the random values stored in the receiver buffer by the same defined amount as in the transmitter buffer so that a random value at one end of the receiver buffer drops out of the buffer and a position at the other end of the receiver buffer becomes free; i) storing the second result in the position in the receiver buffer that has become free; and j) in response to a transmission error, reducing the logical buffer size of each of said buffers to correspond to a secure area in which values remain synchronized with corresponding values in the other buffer.