Patent Grant
7242770
This invention relates to secure encryption/decryption protocol for elevator displays and controls. The protocol uses an algorithm to scramble information before transmission and reassemble it after transmission.
Data encryption provides security for transmitted data by scrambling the “clear text” data into “scrambled text”. Typically, the transmitted data is scrambled in a manner selected by a unique key value. For example, this could be a 56-bit binary number. This then is unscrambled at the receiving station by a reverse process.
The present invention relates to a communication device for an elevator control system. The communication device performs data communication in a data communication network of the elevator control system.
More specifically, the communication protocol sends information to the elevators displays and controls. In the past, the format was extremely straightforward and easy to comprehend. Because of the straightforward manner in which the protocol was carried out, it was very insecure. A method and apparatus for generating secure elevator protocols was needed.
The process and apparatus of this invention uses a secure communication in an elevator display and control systems. A primary controller provides information or controls the internal operations of at least one elevator. The system uses at least one block of data assembled into unencrypted N-bits of information, and an encryption device that encodes the data into at least one block of encrypted M-bits of information. A data encryption mask defines an encryption routine for placing the N-bits of information into M-bits of information using an algorithm. A transmitter transmits encrypted data from the primary controller of an elevator; and a decryption algorithm decodes the encrypted information into unencrypted information.
Within the old protocol, three basic packets were transmitted, a floor packet, a message packet, and a travel packet.
The floor packet could be broken down in to a floor header, a floor number, three ASCII characters describing the floor (i.e. LBY for Lobby), and some miscellaneous bits. The message packet would contain a message header, message number, three message characters, and some message bits. The travel packet would contain floor numbers, message numbers and single bits each representing a flag for a particular event like door strobes, chimes, up arrows, down arrows, and the like.
As mentioned above, these data packets were very insecure. It would be a simple matter for a person of skill to pick apart the data and discover how to use it. The ASCII information is especially easy to comprehend.
During the encryption, a data encryption mask is employed. The data encryption mask defines the encryption routine where all of the data bits should be placed. There are several data encryption masks. The decoding key bits make up a word that describes which mask was used during the encryption process.
In order to reassemble the information, an algorithm receives all three encrypted packets, determine which packet is which based upon the type nibble, resolves which encryption mask was employed when the data was scrambled, and then uses that same encryption mask to decipher the data and place it back into the floor, message and travel packets.
In a preferred embodiment, the primary controller controls operations of a plurality of elevators and a plurality of subordinate controllers controls inputs to and outputs from the elevators. The system works well with a single elevator as well as multiple elevators.
Encoding Description:
Prior to encoding any of the information, the data is assembled into 28 bits of floor information, 28 bits of message information, and 28 bits of travel information. These packets are very similar to the old packets where the floor packet would consist of a floor number, floor ASCII, and some miscellaneous bits. The other two packets are similar as well.
Then, the data is encoded into three 40-bit packets. These encoded packets are comprised of a start bit, type nibble (4-bits), decoding key bit, encrypted data, decoding key bit, checksum, and a stop bit. The type bits and the decoding key bits are not encrypted.
During the encryption, a data encryption mask is employed. The data encryption mask defines to the encryption routine where all of the data bits should be placed. There are several data encryption masks. The decoding key bits make up a word that describes which mask was used during the encryption process.
Bits from the structured 28-bit floor packet are scattered across all three of the encoded messages inside the encrypted portion of the data. The organized message and travel packets are scattered across the encoded messages in a similar fashion.
When the encryption is complete, three 40-bit packets house all of the floor, message and travel information. However all of the data has been scrambled based upon the encryption mask.
Decoding Description:
In order to reassemble the information, an algorithm will need receive all three encrypted packets, determine which packet is which based upon the type nibble, resolve which encryption mask was employed when the data was scrambled, and then use that same encryption mask to decipher the data and place it back into the floor, message and travel packets.
Prior to encoding and after decoding the Floor Packet looks like this:
Prior to encoding and after decoding the Message Packet looks like this:
Prior to encoding and after decoding the Travel Packet looks like this:
Three packets for transmission after Encryption:
In addition to these embodiments, persons skilled in the art can see that numerous modifications and changes may be made to the above invention without departing from the intended spirit and scope thereof.
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