Authenticating nonces prior to encrypting and decrypting cryptographic keys
Data security is enhanced by receiving a request that identifies an encrypted data key, an authentication tag, and additional authenticated data that includes at least a nonce. In some cases, the authentication tag is cryptographically derivable from the encrypted data key and the additional authenticated data. A system, in some cases, determines whether the nonce is authentic and decrypts the encrypted data key by using at least a cryptographic key and the nonce, thereby resulting in a plaintext data key that is usable in various contexts.
1. A computer-implemented method, comprising:
at a first computing entity:
obtaining, from a web service application programming interface request from a second computing entity, an encrypted first key, a nonce generated by the second computing entity, and an authentication tag, wherein the authentication tag is derived using a keyed hash function based at least in part on the first key as a secret of the keyed hash function and a message that comprises the encrypted first key and the nonce;
authenticating the nonce based at least in part on the authentication tag; and
contingent upon successfully verifying authenticity of the nonce, decrypting the encrypted first key using a second key and the nonce.
2. The computer-implemented method of claim 1 , wherein the authentication tag is a first authentication tag and authenticating the nonce comprises:
computing a second authentication tag, where the computing of the second authentication tag is based at least in part on the encrypted first key and the nonce;
comparing the first authentication tag and the second authentication tag; and
detecting the first authentication tag and the second authentication tag match.
3. The computer-implemented method of claim 1 , further comprising:
at the first computing entity:
decrypting an encrypted data using the first key and the nonce, thereby generating plaintext data; and
providing the plaintext data to the second computing entity.
4. The computer-implemented method of claim 1 , wherein the message comprises the first key in an encrypted format and the nonce.
5. A system, comprising one or more non-transitory machine-readable mediums storing a set of instructions, which if performed by one or more processors, cause the system to at least:
obtain, through a web service application programming interface request from an entity, an encrypted first key, a nonce generated by the entity, and an authentication tag, wherein the first key is used by a keyed hash function to generate the authentication tag from an input comprising the encrypted first key and the nonce;
determine the nonce is authentic based at least the authentication tag; and
decrypt, as a result of authentication of the nonce, the encrypted first key by at least using a second key and the nonce.
6. The system of claim 5 , wherein the set of instructions to determine that the nonce is authentic further include instructions that, as a result of execution by the one or more processors, cause the system to compare the authentication tag to a second authentication tag computed based at least in part on the encrypted first key and the nonce.
7. The system of claim 5 , wherein the set of instructions include instructions that, as a result of execution by the one or more processors, cause the system to provide the decrypted first key and the nonce for input into a decryption algorithm to decrypt encrypted data in response to determining the nonce is authentic.
8. The system of claim 5 , wherein the set of instructions to decrypt the encrypted first key by at least using the second key and the nonce include instructions that, as a result of execution by the one or more processors, cause the system to initialize an initialization vector using the nonce.
9. The system of claim 5 , wherein the set of instructions include instructions that, as a result of execution by the one or more processors, cause the system to decrypt the encrypted first key using an authenticated encryption mode of a cryptographic algorithm, wherein the authenticated encryption mode is in accordance with a block cipher mode of operation.
10. The system of claim 9 , wherein the block cipher mode of operation is Galois/Counter (GCM) mode.
11. The system of claim 5 , wherein the encrypted first key, the authentication tag, and the nonce are obtained in a request obtained from a requestor over a network.
12. The system of claim 5 , wherein the set of instructions include instructions that, as a result of execution by the one or more processors, cause the system to generate the nonce and the encrypted first key.
13. A non-transitory computer-readable storage medium storing thereon executable instructions that, as a result of execution by one or more processors of a computer system, cause the computer system to at least:
obtain, from a web service application programming interface request from a different computer system, an encrypted first key, a nonce generated by the different computer system, and an authentication tag, wherein the first key is used in a keyed hash function to generate the authentication tag from a message comprising the encrypted first key and the nonce;
determine the nonce is authentic based at least the authentication tag; and
based at least in part on determining the nonce is authentic, decrypt the encrypted first key by at least using a second key and the nonce.
14. The non-transitory computer-readable storage medium of claim 13 , further comprising instructions that, as a result of execution by the one or more processors, cause the computer system to:
compute a second authentication tag, where the computing of the second authentication tag is based at least in part on the encrypted first key and the nonce;
compare the authentication tag and the second authentication tag;
detect the authentication tag and the second authentication tag match; and
make the decrypted first key and the nonce available for use in response to determining the authentication tag and the second authentication tag match.
15. The non-transitory computer-readable storage medium of claim 13 , further comprising instructions that, as a result of execution by the one or more processors, cause the computer system to provide the decrypted first key and the nonce for input into a decryption algorithm to decrypt data.
16. The non-transitory computer-readable storage medium of claim 13 , wherein the authentication tag is derived based at least in part on the encrypted first key, the nonce, and additional authenticated data.
17. The non-transitory computer-readable storage medium of claim 13 , wherein the authentication tag is a hash-based message authentication code.
18. The non-transitory computer-readable storage medium of claim 13 , further comprising instructions that, as a result of execution by the one or more processors, cause the computer system to:
obtain a second request to decrypt the encrypted first key;
verify authenticity of the nonce; and
provide the decrypted first key in response to the second request as a result of the authenticity of the nonce being verified.
19. The non-transitory computer-readable storage medium of claim 13 , wherein the authentication tag is derived further based at least in part on a ciphertext.
20. The non-transitory computer-readable storage medium of claim 13 , further comprising instructions that, as a result of execution by the one or more processors, cause the computer system to cryptographically hash the encrypted first key and the nonce, thereby deriving the authentication tag.