Using a single instruction multiple data (SIMD) instruction to speed up galois counter mode (GCM) computations

1. A method comprising:

multiplying a most significant portion of a product of a carry-less multiplication performed using a first single instruction multiple data (SIMD) multiplication instruction in a processor with a first value to generate a second value in the processor;

multiplying a most significant portion of the second value with a least significant portion of an irreducible polynomial of a final field used in a block cipher to generate a third value in the processor;

determining a remainder based on the third value; and

generating a signal based on a value of the remainder, wherein the value of the remainder indicates whether an encrypted message is authentic in accordance with a Galois Counter Mode (GCM), wherein the first value comprises a quotient from a division of 2 256 with the irreducible polynomial of the final field used in the block cipher in accordance with the GCM.

2. The method of claim 1 , further comprising executing a plurality of the first SIMD multiplication instruction in a SIMD unit of the processor to obtain the product of the carry-less multiplication, wherein each of the plurality of the first SIMD multiplication instruction is associated with a different immediate datum.

3. The method of claim 2 , wherein each of the plurality of the first SIMD multiplication instruction is to execute on a portion of a first operand and a second operand responsive to the immediate datum associated with the corresponding first SIMD multiplication instruction.

4. The method of claim 3 , further comprising storing a temporary product of each of the plurality of the first SIMD multiplication instruction in a corresponding SIMD register of the processor.

5. The method of claim 4 , further comprising exclusive-OR-ing (XOR) a first temporary product and a second temporary product according to a second SIMD instruction and shuffling the XOR result according to a third SIMD instruction.

6. The method of claim 5 , further comprising accessing the first temporary product and the second temporary product directly from the corresponding SIMD registers and without a scalar domain-to-SIMD domain crossing.

7. The method of claim 1 , further comprising left shifting the product of the carry-less multiplication to accommodate a bit reflection property of the GCM.

8. The method of claim 1 , further comprising performing the first multiplying and the second multiplying according to a linear folding algorithm.

9. A non-transitory computer-readable storage medium comprising one or more instructions that when executed on a processor enable the processor to:

multiply a most significant portion of a product of a carry-less multiplication performed using a first single instruction multiple data (SIMD) multiplication instruction with a first value to generate a second value;

multiply a most significant portion of the second value with a least significant portion of an irreducible polynomial of a final field used in a block cipher to generate a third value;

determine a remainder based on the third value; and

generate a signal based on a value of the remainder, wherein the value of the remainder indicates whether an encrypted message is authentic in accordance with Galois Counter Mode (GCM).

10. The non-transitory computer-readable storage medium of claim 9 , further comprising instructions that enable the processor to execute a plurality of the first SIMD multiplication instruction in a SIMD unit of the processor to obtain the product of the carry-less multiplication, wherein each of the plurality of the first SIMD multiplication instruction is associated with a different immediate datum.

11. The non-transitory computer-readable storage medium of claim 10 , wherein each of the first SIMD multiplication instructions is to execute on a portion of a first operand and a second operand responsive to the immediate datum associated with the corresponding first SIMD multiplication instruction.

12. The non-transitory computer-readable storage medium of claim 11 , further comprising instructions that enable the processor to store a temporary product of each of the plurality of first SIMD multiplication instructions in a corresponding SIMD register.

13. The non-transitory computer-readable storage medium of claim 12 , further comprising instructions that enable the processor to exclusive-OR (XOR) a first temporary product and a second temporary product according to a second SIMD instruction and shuffle the XOR result according to a third SIMD instruction.

14. A system comprising:

a processor including an encryption module to obtain a product of a carry-less multiplication using a plurality of first single instruction multiple data (SIMD) multiplication instructions each to execute on a portion of a first operand and a second operand responsive to an immediate datum associated with the corresponding first SIMD multiplication instruction, and to reduce the product modulo g to form a message authentication code of a mode of a block cipher;

a memory coupled to the processor to store the plurality of first SIMD multiplication instructions;

wherein the encryption module includes a SIMD unit to execute the plurality of SIMD multiplication instructions;

wherein the encryption module is to store a temporary product of each of the plurality of first SIMD multiplication instructions in a corresponding SIMD register; and

wherein the encryption module is to exclusive-OR (XOR) a first temporary product and a second temporary product according to a second SIMD instruction and shuffle the XOR result according to a third SIMD instruction.

15. The system of claim 14 , wherein the encryption module is to access the first temporary product and the second temporary product directly from the corresponding SIMD registers and without a scalar domain-to-SIMD domain crossing.

16. The system of claim 14 , wherein the encryption module is to form the message authentication code according to a linear folding algorithm for a reflected version of g.