Low latency block cipher in memory devices
A storage device includes multiple memory dies and a controller configured to: (i) encrypt a data block using a key schedule that includes a plurality of round keys generated from an encryption key, the encrypting resulting in an encrypted data block; (ii) during the encrypting, modify a key register during a first plurality of iterations, the key register being updated to a final state of the key register after a final iteration of the plurality of iterations; (iii) store the final state of the key register as a decryption key; and (iv) decrypt the encrypted data block using another key schedule that includes the plurality of round keys that are generated using the decryption key during a second plurality of iterations.
1. A method, comprising:
encrypting a data block using a first key schedule that includes a plurality of round keys generated from an encryption key, the encrypting resulting in an encrypted data block;
during the encrypting, modifying a key register during a first plurality of iterations, the key register being updated to a final state after a final iteration of the plurality of iterations, and wherein modifying the key register for each of the first plurality of iterations comprises:
cyclically rotating bits of the key register a predetermined number of positions;
performing a non-linear substitution operation on a first predetermined number of bits in a first set of predetermined bit positions of the key register; and
performing an exclusive-or (XOR) operation between (i) a second predetermined number of bits in a second set of predetermined bit positions of the key register and (ii) a value of a round counter for the first plurality of iterations;
storing the final state of the key register as a decryption key; and
decrypting the encrypted data block using a second key schedule that includes the plurality of round keys that are generated using the decryption key during a second plurality of iterations.
2. The method of claim 1 , wherein decrypting the encrypted data block further comprises:
storing the decryption key into the key register;
initiating the second plurality of iterations starting at a last iteration value and decreasing to a first iteration value; and
during each iteration of the second plurality of iterations:
updating the key register based, at least in part, on a current iteration value; and
generating a round key from the key register using a first number of most significant bits of the key register.
3. The method of claim 2 , wherein decrypting the encrypted data block further comprises:
storing the encrypted data block in a data register; and
during each iteration of the second plurality of iterations:
applying the generated round key to the data register by performing an exclusive-or (XOR) operation on the data register using the generated round key.
4. The method of claim 2 , wherein updating the key register based, at least in part, on the current iteration value further comprises:
performing an exclusive-or (XOR) operation between (i) a first predetermined number of bits in a first set of predetermined bit positions of the key register and (ii) a value of a round counter for the second plurality of iterations;
performing an inverse non-linear substitution operation on a second predetermined number of bits in a second set of predetermined bit positions of the key register; and
cyclically rotating bits of the key register a predetermined number of bit positions in a predetermined direction.
5. The method of claim 1 , wherein cyclically rotating bits of the key register a predetermined number of positions comprises cyclically rotating the bits of the key register the predetermined number of bit positions in a predetermined direction.
6. The method of claim 1 , further comprising:
during each iteration of the first plurality of iterations:
performing an encrypting operation using a round counter previously generated from the key register; and
in parallel with the performing of the encryption, generating a next round counter using the key register, the next round counter to be used during a next iteration.
7. The method of claim 1 , further comprising, during the encrypting:
storing the encryption key into the key register;
generating a first round key;
initiating the first plurality of iterations starting at a first iteration value and increasing to a last iteration value; and
during each iteration of the first plurality of iterations:
performing an encrypting operation using a round counter previously generated; and
in parallel with the performing of the encryption, generating a next round counter using the key register to be used during a next iteration.
8. A storage device, comprising:
a non-volatile storage device comprising a plurality of memory dies, the non-volatile storage device including a plurality of memory cells; and
a controller communicatively coupled to the non-volatile storage device and configured to:
encrypt a data block using a first key schedule that includes a plurality of round keys generated from an encryption key, the encrypting resulting in an encrypted data block;
during the encrypting, modify a key register during a first plurality of iterations, the key register being updated to a final state after a final iteration of the plurality of iterations and wherein modifying the key register during each of the first plurality of iterations comprises:
cyclically rotating bits of the key register a predetermined number of positions;
performing a non-linear substitution operation on a first predetermined number of bits in a first predetermined set of bit positions of the key register; and
performing an exclusive-or (XOR) operation between (i) a second predetermined number of bits in a second set of predetermined bit positions of the key register and (ii) a value of a round counter for the first plurality of iterations;
store the final state of the key register as a decryption key; and
decrypt the encrypted data block using a second key schedule that includes the plurality of round keys that are generated using the decryption key during a second plurality of iterations.
9. The storage device of claim 8 , wherein decrypting the encrypted data block further comprises:
storing the decryption key into the key register;
initiating the second plurality of iterations starting at a last iteration value and decreasing to a first iteration value; and
during each iteration of the second plurality of iterations:
updating the key register based, at least in part, on a current iteration value; and
generating a round key from the key register using a first number of most significant bits of the key register.
10. The storage device of claim 9 , wherein decrypting the encrypted data block further comprises:
storing the encrypted data block in a data register; and
during each iteration of the second plurality of iterations:
apply the generated round key to the data register by performing an exclusive-or (XOR) operation on the data register using the generated round key.
11. The storage device of claim 9 , wherein updating the key register based, at least in part, on the current iteration value further comprises:
performing an exclusive-or (XOR) operation between (i) a first predetermined number of bits in a first set of predetermined bit positions of the key register and (ii) a value of a round counter for the second plurality of iterations;
performing an inverse non-linear substitution operation on a second predetermined number of bits in a second set of predetermined bit positions of the key register; and
cyclically rotating bits of the key register a predetermined number of bit positions in a predetermined direction.
12. The storage device of claim 8 , wherein cyclically rotating bits of the key register a predetermined number of positions comprises cyclically rotating the bits of the key register the predetermined number of bit positions in a predetermined direction.
13. The storage device of claim 8 , wherein the controller is further configured to:
during each iteration of the first plurality of iterations:
perform an encrypting operation using a round counter previously generated from the key register; and
in parallel with the performing of the encryption, generate a next round counter using the key register to be used during the next iteration.
14. The storage device of claim 8 , wherein the controller is further configured to, during the encrypting:
store the encryption key into the key register;
generate a first round key;
initiate the first plurality of iterations starting at a first iteration value and increasing to a last iteration value; and
during each iteration of the first plurality of iterations:
perform an encrypting operation using a round counter previously generated; and
in parallel with the performing of the encryption, generate a next round counter using the key register to be used during the next iteration.
15. A storage device, comprising:
a non-volatile storage device comprising a plurality of memory dies, the non-volatile storage device including a plurality of memory cells; and
means for encrypting a data block using a first key schedule that includes a plurality of round keys generated from an encryption key, the encrypting resulting in an encrypted data block;
means for modifying a key register during a first plurality of iterations, the key register being updated to a final state after a final iteration of the plurality of iterations, the means for modifying the key register comprising:
means for cyclically rotating bits of the key register a predetermined number of positions;
means for performing a non-linear substitution operation on a first predetermined number of bits in first predetermined bit positions of the key register; and
means for performing an exclusive-or (XOR) operation between (i) a second predetermined number of bits in second predetermined bit positions of the key register and (ii) a value of a round counter for the first plurality of iterations;
means for storing the final state of the key register as a decryption key; and
means for decrypting the encrypted data block using a second key schedule that includes the plurality of round keys that are generated using the decryption key during a second plurality of iterations.
16. The storage device of claim 15 , wherein decrypting the encrypted data block further comprises:
means for storing the decryption key into the key register;
means for initiating the second plurality of iterations starting at a last iteration value and decreasing to a first iteration value; and
during each iteration of the second plurality of iterations:
means for updating the key register based, at least in part, on a current iteration value; and
means for generating a round key from the key register using a first number of most significant bits of the key register.
17. The storage device of claim 16 , wherein decrypting the encrypted data block further comprises:
means for storing the encrypted data block in a data register; and
during each iteration of the second plurality of iterations:
means for applying the generated round key to the data register by performing an exclusive-or (XOR) operation on the data register using the generated round key.
18. The storage device of claim 16 , wherein updating the key register based, at least in part, on the current iteration value further comprises:
means for performing an exclusive-or (XOR) operation between (i) a first predetermined number of bits in predetermined bit positions of the key register and (ii) a value of a round counter for the second plurality of iterations;
means for performing an inverse non-linear substitution operation on a second predetermined number bits in a second set of predetermined bit positions of the key register; and
means for cyclically rotating bits of the key register a predetermined number of bit positions in a predetermined direction.
19. The storage device of claim 15 , further comprising:
during each iteration of the first plurality of iterations:
means for performing an encrypting operation using a round counter previously generated from the key register; and
in parallel with the performing of the encryption, means for generating a next round counter using the key register to be used during the next iteration.
20. The storage device of claim 15 , further comprising, during the encrypting:
means for storing the encryption key into the key register;
means for generating a first round key;
means for initiating the first plurality of iterations starting at a first iteration value and increasing to a last iteration value; and
during each iteration of the first plurality of iterations:
means for performing an encrypting operation using a round counter previously generated; and
in parallel with the performing of the encryption, means for generating a next round counter using the key register to be used during the next iteration.