Apparatus and method for key scheduling
AssigneeWinbond Electronics Corp.
InventorZiv Leshem
Life of this patent
Estimating the term…
Abstract
A key scheduler for encryption/decryption produces a new ciphering key by a key expansion process or recovers a previous ciphering key by an inverse expansion process. The key scheduler includes a set of adders and transformation circuitry. Each of adders receives a portion of a round key value as its first input. Some of the adders receive either a portion of the round key value or the output of some of the adders, as its second input, be control of arbitration devices. One adder receives as its second input an output from the transformation circuitry, which output is selected by an arbitration device from either a portion of the round key value or an output of an adder. The selection done by the arbitration devices depending on whether the process desired is the key expansion or inverse expansion.
Claims20
A key scheduler for at least one of 1) producing a new ciphering key by a key expansion process and 2) recovering a previous ciphering key by an inverse expansion process utilizing a round key value, the scheduler comprising:
- a set of adders, each adder receiving a first input comprising a portion of the round key value and a second input;
- transformation circuitry for producing reversible digital transformation of an input of the transformation circuitry, an output of the transformation circuitry provided to one of the adders as its second input;
- and
- a first set of arbitration devices, each of which selects between a first input comprising the portion of the round key value received by a particular one of the adders and a second input comprising an output of the particular one of the adders, wherein an output of one of the arbitration devices provides the input to the transformation circuitry, and an output of each remaining arbitration device provides the second input of one of the adders.
An apparatus for at least one of 1) producing a new ciphering key by a key expansion process and 2) recovering a previous ciphering key by an inverse expansion process, the apparatus comprising:
- a first arbitration device having a first input for receiving a first portion of a first key and having a second input for receiving a first portion of a second key, the first arbitration device selecting the first input or second input as an output of the first arbitration device in response to a control signal;
- a second arbitration device having a first input for receiving a second portion of the first key and having a second input for receiving a second portion of the second key, the second arbitration device selecting the first input or second input as an output of the second arbitration device in response to the control signal;
- a third arbitration device having a first input for receiving a third portion of the first key and having a second input for receiving a third portion of the second key, the third arbitration device selecting the first input or second input as an output of the third arbitration device in response to the control signal;
- a fourth arbitration device having a first input for receiving a fourth portion of the first key and having a second input for receiving a fourth portion of the second key, the fourth arbitration device selecting the first input or second input as an output of the fourth arbitration device in response to the control signal;
- a transformation circuit receiving the output of the first arbitration device and producing a transformed output;
- a first adder having a first input for receiving the first portion of the first key and a second input for receiving the output of the second arbitration device;
- a second adder having a first input for receiving the second portion of the first key and a second input for receiving the output of the third arbitration device;
- a third adder having a first input for receiving the third portion of the first key and a second input for receiving the output of the fourth arbitration device;
- and
- a fourth adder having a first input for receiving the fourth portion of the first key and a second input for receiving the transformed output of the transformation circuit;
- wherein each adder outputs a respective portion of the second key, and the control signal controls whether the adders produce the new ciphering key or recover the previous ciphering key.
A method for at least one of 1) producing a new ciphering key by a key expansion process and 2) recovering a previous ciphering key by an inverse expansion process, comprising:
- receiving a first round key value as a first input to a first portion and a second portion of an adder;
- receiving a first portion of the first round key value as a first input to a first arbitration device and a first portion of a second round key value as a second input to the first arbitration device;
- selecting the first portion of the first round key value or the first portion of the second round key value as an output of the first arbitration device depending on whether a desired process is the expansion process or the inverse expansion process;
- transforming the output of the first arbitration device to produce a transformed output;
- receiving the transformed output as a second input to the first portion of the adder;
- receiving a second portion of the first round key value as a first input to a second arbitration device and a second portion of the second round key value as a second input to the second arbitration device;
- selecting the second portion of the first round key value or the second portion of the second round key value as an output of the second arbitration device depending on whether the desired process is the expansion process or the inverse expansion process;
- and
- receiving the output of the second arbitration device as a second input to the second portion of the adder;
- wherein the adder outputs the second round key value.
A communications device operable for communicating with a network, the communications device comprising:
- a key scheduler capable of at least one of:
- producing a new ciphering key by a key expansion process and recovering a previous ciphering key by an inverse expansion process utilizing a round key value, the key scheduler comprising:
- a set of adders, each adder receiving a first input comprising a portion of the round key value and a second input,
- transformation circuitry for producing reversible digital transformation of an input of the transformation circuitry, an output of the transformation circuitry provided to one of the adders as its second input;
- and
- a first set of arbitration devices, each of which selects between a first input comprising the portion of the round key value received by a particular one of the adders and a second input comprising an output of the particular one of the adders, wherein an output of one of the arbitration devices provides the input to the transformation circuitry, and an output of each remaining arbitration device provides the second input of one of the adders.
Dependencies are inferred from the claim text.