Cryptographic architecture for cryptographic permutation
Cryptographic methods and systems are described. Certain examples relate to performing cryptographic operations that involve a cryptographic permutation. The methods and systems may be used to provide cryptographic functions such as hashing, encryption, decryption and random number generation. In one example, a cryptographic architecture is provided. The cryptographic architecture has a processor interface comprising a set of cryptographic registers, where the processor interface is accessible by at least one processing unit. The cryptographic architecture also has a cryptographic permutation unit comprising circuitry to perform a cryptographic permutation using data stored within the set of cryptographic registers. In examples, the at least one processing unit instructs the cryptographic permutation and accesses a result of the cryptographic permutation using the processor interface.
1 . A cryptographic architecture comprising:
a processor interface comprising a set of cryptographic registers, the processor interface being accessible by at least one processing unit, the at least one processing unit being separate from the cryptographic architecture; and
cryptographic permutation circuitry configured to perform a cryptographic permutation using data stored within the set of cryptographic registers,
wherein the at least one processing unit instructs the cryptographic architecture to perform the cryptographic permutation and accesses a result of the cryptographic permutation using the processor interface,
wherein the set of cryptographic registers comprise:
one or more control registers that are accessible to the at least one processing unit;
a permutation state register to store a permutation state;
a permutation input register to store permutation input data, the permutation input register being writable by the at least one processing unit;
a permutation output register to store output data, the permutation output register being readable by the at least one processing unit, wherein the permutation state is not visible to the at least one processing unit;
a mask input register to store an input mask, the mask input register being writable by the at least one processing unit;
permutation masking circuitry, communicatively coupled to the mask input register and the permutation state register, to apply an AND operation to data derived from the input mask and data derived from permutation data from the permutation state register; and
input application circuitry, communicatively coupled to the permutation masking circuitry and the permutation input register, to apply an XOR operation to data derived from the permutation masking circuitry and data derived from the permutation input data, the input application circuitry being configured to supply output data to the cryptographic permutation circuitry;
wherein the cryptographic architecture is configured to indicate a completion of the cryptographic permutation by setting a control flag within the control registers.
2 . The cryptographic architecture of claim 1 , wherein the cryptographic architecture is configured to perform the cryptographic permutation based on a single machine code instruction that is executed by the at least one processing unit.
3 . The cryptographic architecture of claim 2 , wherein the single machine code instruction is implemented as an Instruction Set Architecture (ISA) extension.
4 . The cryptographic architecture of claim 1 , wherein the processor interface comprises a plurality of registers configured to store at least b-bits, where b is a size in bits of a permutation input.
5 . The cryptographic architecture of claim 1 , wherein the cryptographic permutation circuitry is configured to perform a KECCAK-p permutation.
6 . The cryptographic architecture of claim 1 , wherein the cryptographic permutation circuitry is configured to perform a keyless permutation comprising a plurality of rounds.
7 . The cryptographic architecture of claim 1 , wherein the at least one processing unit is able to use the cryptographic architecture to perform one or more of the following:
an absorb cryptographic operation to mix input data with a permutation state;
a squeeze cryptographic operation to obtain an output using the permutation state;
an encrypt cryptographic operation to encrypt input data using the permutation state; and
a decrypt cryptographic operation to decrypt input data using the permutation state.
8 . The cryptographic architecture of claim 1 , comprising:
input XOR circuitry to apply an input XOR operation, the input XOR operation being applied to data derived from the permutation input data in the permutation input register and data derived from the permutation state in the permutation state register,
wherein the input XOR circuitry is communicatively coupled to an XOR output register to store an output of the input XOR circuitry.
9 . The cryptographic architecture of claim 1 , wherein, following performance of the cryptographic permutation by the cryptographic permutation circuitry, an output of the cryptographic permutation circuitry is copied to the permutation state register.
10 . The cryptographic architecture of claim 1 , wherein the one or more control registers comprise one or more of:
an identifier register, writable by the at least one processing unit, to store an identifier of a cryptographic operation to be performed;
a start register, writable by the at least one processing unit, to store a start flag for the cryptographic operation;
a ready register, readable by the at least one processing unit, to store a ready flag indicating that the cryptographic architecture is ready to start another cryptographic operation;
one or more round registers, writable by the at least one processing unit, to store one or more flags relating to rounds of cryptographic permutation; and
an interrupt control register, writable by the at least one processing unit, to control interrupts to the at least one processing unit.
11 . The cryptographic architecture of claim 1 , wherein the cryptographic architecture is useable by the at least one processing unit to perform a cryptographic permutation for a SHA-3 function.
12 . A method of performing a cryptographic operation comprising:
receiving, at a cryptographic architecture, an instruction to perform the cryptographic operation from a processing unit, the processing unit being separate from the cryptographic architecture, the cryptographic architecture comprising a set of cryptographic registers comprising one or more control registers that are accessible to the at least one processing unit, wherein receiving said instruction comprises:
accessing a control register of the cryptographic architecture to determine whether a start flag has been set by the processing unit to indicate a start of the cryptographic operation;
loading, by a cryptographic permutation circuitry of the cryptographic architecture, a permutation state from a permutation state register;
loading, by the cryptographic permutation circuitry, permutation input data from a permutation input register, the permutation input data being written under the control of the processing unit;
loading, by the cryptographic permutation circuitry, mask input data from a mask input register;
updating, by the cryptographic architecture, the permutation state in the permutation state register of the set of cryptographic registers by performing an XOR operation as a function of the permutation input data and a result of an AND operation performed on the mask input data and the permutation state to generate updated data;
performing, using the cryptographic permutation circuitry, a cryptographic permutation on the updated data;
storing, by the cryptographic architecture, an output of the cryptographic permutation into the permutation state register; and
indicating, by the cryptographic architecture, to the at least one processing unit that the permutation is complete, wherein the processing unit accesses the output of the cryptographic permutation from the set of cryptographic registers, said indicating comprising setting a control flag within the control registers.
13 . The method of claim 12 , comprising:
reading, by the processing unit, the output of the cryptographic permutation from the set of cryptographic registers.
14 . The method of claim 12 , comprising:
loading, by the cryptographic permutation circuitry from a round control register, a round count;
using, by the cryptographic permutation circuitry, the round count in the cryptographic permutation; and
incrementing the round count in the round control register,
wherein the loading, using and incrementing operations are repeated based on a comparison of the round control register and an end control register.
15 . The cryptographic architecture of claim 1 , wherein the set of cryptographic registers are memory mapped to the address space of the at least one processing unit.