Alibaba Cloud Key Management Service (KMS) is a cloud-based cryptographic key management platform that enables organizations to protect, manage, use, and audit cryptographic keys on Alibaba Cloud. It provides fully managed key lifecycle management, including key generation, rotation, enabling/disabling, and deletion. KMS supports Bring Your Own Key (BYOK) imports into managed HSMs that have passed FIPS 140-2 Level 3 validation. It integrates with a wide range of Alibaba Cloud services such as ECS, RDS, OSS, NAS, and MaxCompute to provide native data encryption. KMS offers envelope encryption, authenticated encryption with associated data (AEAD), and asymmetric key-based digital signature verification. Authentication and authorization are managed through RAM (Resource Access Management), while key usage is audited via ActionTrail, with logs storable in OSS or Log Service for SIEM integration. KMS supports custom key rotation policies, secret management for AK/SK credentials and passwords, and hardware KMS instances for high-assurance environments. It operates on a pay-as-you-go billing model with a minimum price of USD 4.5 per day per instance. SDKs are available in Java, Go, PHP, and Python for application-level encryption scenarios.