Data protection in Amazon Key Management Service - Amazon Key Management Service
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Data protection in Amazon Key Management Service

Amazon Key Management Service stores and protects your encryption keys to make them highly available while providing you with strong and flexible access control.

Data encryption

The data in Amazon KMS consists of Amazon KMS keys and the encryption key material they represent. This key material exists in plaintext only within Amazon KMS hardware security modules (HSMs) and only when in use. Otherwise, the key material is encrypted and stored in durable persistent storage.

The key material that Amazon KMS generates for KMS keys never leaves the boundary of Amazon KMS HSMs unencrypted. It is not exported or transmitted in any Amazon KMS API operations. The exception is for multi-Region keys, where Amazon KMS uses a cross-Region replication mechanism to copy the key material for a multi-Region key from an HSM in one Amazon Web Services Region to an HSM in a different Amazon Web Services Region. For details, see Replication process for multi-Region keys in Amazon Key Management Service Cryptographic Details.

Encryption at rest

Amazon KMS generates key material for Amazon KMS keys in FIPS 140-2 Level 2–compliant hardware security modules (HSMs). The only exception is China Regions, where the HSMs that Amazon KMS uses to generate KMS keys comply with all pertinent Chinese regulations, but are not validated under the FIPS 140-2 Cryptographic Module Validation Program. When not in use, key material is encrypted by an HSM key and written to durable, persistent storage. The key material for KMS keys and the encryption keys that protect the key material never leave the HSMs in plaintext form.

Encryption and management of key material for KMS keys is handled entirely by Amazon KMS.

For more details, see Working with Amazon KMS keys in Amazon Key Management Service Cryptographic Details.

Encryption in transit

Key material that Amazon KMS generates for KMS keys is never exported or transmitted in Amazon KMS API operations. Amazon KMS uses key identifiers to represent the KMS keys in API operations. Similarly, key material for KMS keys in Amazon KMS custom key stores is non-exportable and never transmitted in Amazon KMS or Amazon CloudHSM API operations.

However, some Amazon KMS API operations return data keys. Also, customers can use API operations to import key material for selected KMS keys.

All Amazon KMS API calls must be signed and be transmitted using Transport Layer Security (TLS). Amazon KMS supports TLS 1.0—1.3 and hybrid post-quantum TLS for Amazon KMS service endpoints in all regions, except Amazon GovCloud (US) and China Regions. The Amazon GovCloud (US) and China Regions only support TLS 1.0—1.2 for Amazon KMS service endpoint. The Amazon GovCloud (US) and China Regions do not support hybrid post-quantum TLS. Amazon KMS recommends you always use the latest supported TLS version. Calls to Amazon KMS also require a modern cipher suite that supports perfect forward secrecy, which means that compromise of any secret, such as a private key, does not also compromise the session key.

If you require FIPS 140-2 validated cryptographic modules when accessing Amazon through a command line interface or an API, use a FIPS endpoint. Amazon KMS supports version 1.2 of Transport Layer Security (TLS) for FIPS endpoints for select regions. For more information about the available FIPS endpoints, see Federal Information Processing Standard (FIPS) 140-2. For a list of Amazon KMS FIPS endpoints, see Amazon Key Management Service endpoints and quotas in the Amazon General Reference.

Communications between Amazon KMS service hosts and HSMs are protected using Elliptic Curve Cryptography (ECC) and Advanced Encryption Standard (AES) in an authenticated encryption scheme. For more details, see Internal communication security in Amazon Key Management Service Cryptographic Details.

Key management

Amazon KMS does not directly store customer data. Instead, Amazon KMS is responsible for storing and protecting Amazon KMS keys, which are logical entities backed by cryptographic key material.

Key material for KMS keys is supported by a distributed fleet of FIPS 140-2 Level-2–validated hardware security modules (HSMs). The only exception is China Regions, where the HSMs that Amazon KMS uses to protect KMS keys comply with all pertinent Chinese regulations, but are not validated under the FIPS 140-2 Cryptographic Module Validation Program. Each Amazon KMS HSM is a standalone cryptographic hardware appliance designed to provide dedicated cryptographic functions to meet the security and scalability requirements of Amazon KMS.

The key material for KMS keys exists in plaintext only inside the HSMs and only when the key material is generated or being used in a cryptographic operation.

When not in use, key material is encrypted on the HSMs and the encrypted key material is written to durable, low-latency persistent storage. The encryption keys that protect the key material never leave the HSMs in plaintext form. There are no mechanisms for anyone, including Amazon service operators, to export or view the key material or HSM encryption keys in plaintext.

Custom key stores, an optional Amazon KMS feature, lets you create KMS keys backed by key material generated in Amazon CloudHSM hardware security modules that you control. These HSMs are certified at FIPS 140-2 Level 3.

Another optional feature lets you import the key material for a KMS key. During transport from its source to Amazon KMS, the imported key material must be encrypted using RSA key pairs generated in Amazon KMS HSMs. The imported key material is decrypted on an Amazon KMS HSM and re-encrypted under symmetric keys in the HSM. These operations are performed before the imported key material is stored with key material generated by Amazon KMS. Once it is imported, the imported key material never leaves the HSMs unencrypted. The customer who provided the key material is responsible for secure use, durability, and maintenance of the key material outside of Amazon KMS.

For details about the management of KMS keys and key material, see Amazon Key Management Service Cryptographic Details

Internetwork traffic privacy

Amazon KMS supports an Amazon Web Services Management Console and a set of API operations that enable you to create and manage Amazon KMS keys and use them in cryptographic operations.

Amazon KMS supports two network connectivity options from your private network to Amazon.

  • An IPSec VPN connection over the internet

  • Amazon Direct Connect, which links your internal network to an Amazon Direct Connect location over a standard Ethernet fiber-optic cable.

All Amazon KMS API calls must be signed and be transmitted using Transport Layer Security (TLS). The calls also require a modern cipher suite that supports perfect forward secrecy. Traffic to the hardware security modules (HSMs) that store key material for KMS keys is permitted only from known Amazon KMS API hosts over the Amazon internal network.

To connect directly to Amazon KMS from your virtual private cloud (VPC) without sending traffic over the public internet, use VPC endpoints, powered by Amazon PrivateLink. For more information, see Connecting to Amazon KMS through a VPC endpoint.

Amazon KMS also supports a hybrid post-quantum key exchange option for the Transport Layer Security (TLS) network encryption protocol. You can use this option with TLS when you connect to Amazon KMS API endpoints.