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AsymmetricDecrypt

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Decrypts data using an asymmetric key.

Operation description

Precautions

  • For details about the access policies that must be granted to a RAM user or RAM role to invoke this operation, see Access control.

  • This operation can be invoked through a shared gateway or a dedicated gateway. For more information, see Alibaba Cloud SDK.

    • Shared gateway: Access KMS using a public endpoint or a VPC endpoint. This method requires you to enable public network access. For more information, see Access keys in a KMS instance over the Internet.

    • Dedicated gateway: Access KMS using a KMS private endpoint (<YOUR_KMS_INSTANCE_ID>.cryptoservice.kms.aliyuncs.com).

QPS limits

  • Calls through a shared gateway: The QPS limit for a single user is 200 calls per second. If this limit is exceeded, API calls are throttled, which may affect your business. Call this operation at a reasonable rate.

  • Calls through a dedicated gateway: The QPS limit for a single user is determined by the performance specifications of your KMS instance. For more information, see Performance data.

Details

Only asymmetric keys with Usage set to ENCRYPT/DECRYPT are supported. The following table lists the supported encryption algorithms:

KeySpecAlgorithmDescriptionCiphertext length (bytes)
RSA_2048RSAES_OAEP_SHA_256RSAES-OAEP using SHA-256 and MGF1 with SHA-256256
RSA_2048RSAES_OAEP_SHA_1RSAES-OAEP using SHA1 and MGF1 with SHA1256
RSA_3072RSAES_OAEP_SHA_256RSAES-OAEP using SHA-256 and MGF1 with SHA-256384
RSA_3072RSAES_OAEP_SHA_1RSAES-OAEP using SHA1 and MGF1 with SHA1384
EC_SM2SM2PKESM2 elliptic curve public key encryption algorithmUp to 6144

This topic provides an example of using an asymmetric key with key ID key-hzz630494463ejqjx**** and key version ID 2ab1a983-7072-4bbc-a582-584b5bd8**** to decrypt the ciphertext BQKP+1zK6+ZEMxTP5qaVzcsgXtWplYBKm0NXdSnB5FzliFxE1bSiu4dnEIlca2JpeH7yz1/S6fed630H+hIH6DoM25fTLNcKj+mFB0Xnh9m2+HN59Mn4qyTfcUeadnfCXSWcGBouhXFwcdd2rJ3n337bzTf4jm659gZu3L0i6PLuxM9p7mqdwO0cKJPfGVfhnfMz+f4alMg79WB/NNyE2lyX7/qxvV49ObNrrJbKSFiz8Djocaf0IESNLMbfYI5bXjWkJlX92DQbKhibtQW8ZOJ//ZC6t0AWcUoKL6QDm/dg5koQalcleRinpB+QadFm894sLbVZ9+N4GVsv1W****== using the decryption algorithm RSAES_OAEP_SHA_1.

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Test

RAM authorization

The table below describes the authorization required to call this API. You can define it in a Resource Access Management (RAM) policy. The table's columns are detailed below:

  • Action: The actions can be used in the Action element of RAM permission policy statements to grant permissions to perform the operation.

  • API: The API that you can call to perform the action.

  • Access level: The predefined level of access granted for each API. Valid values: create, list, get, update, and delete.

  • Resource type: The type of the resource that supports authorization to perform the action. It indicates if the action supports resource-level permission. The specified resource must be compatible with the action. Otherwise, the policy will be ineffective.

    • For APIs with resource-level permissions, required resource types are marked with an asterisk (*). Specify the corresponding Alibaba Cloud Resource Name (ARN) in the Resource element of the policy.

    • For APIs without resource-level permissions, it is shown as All Resources. Use an asterisk (*) in the Resource element of the policy.

  • Condition key: The condition keys defined by the service. The key allows for granular control, applying to either actions alone or actions associated with specific resources. In addition to service-specific condition keys, Alibaba Cloud provides a set of common condition keys applicable across all RAM-supported services.

  • Dependent action: The dependent actions required to run the action. To complete the action, the RAM user or the RAM role must have the permissions to perform all dependent actions.

Action

Access level

Resource type

Condition key

Dependent action

kms:AsymmetricDecrypt

get

*Key

acs:kms:{#regionId}:{#accountId}:key/{#KeyId}
  • kms:tag
 None

Request parameters

Parameter

Type

Required

Description

Example
CiphertextBlob

string

Yes

The ciphertext to decrypt, encoded in Base64.

Note

You can call the AsymmetricEncrypt operation to generate the ciphertext.

BQKP+1zK6+ZEMxTP5qaVzcsgXtWplYBKm0NXdSnB5FzliFxE1bSiu4dnEIlca2JpeH7yz1/S6fed630H+hIH6DoM25fTLNcKj+mFB0Xnh9m2+HN59Mn4qyTfcUeadnfCXSWcGBouhXFwcdd2rJ3n337bzTf4jm659gZu3L0i6PLuxM9p7mqdwO0cKJPfGVfhnfMz+f4alMg79WB/NNyE2lyX7/qxvV49ObNrrJbKSFiz8Djocaf0IESNLMbfYI5bXjWkJlX92DQbKhibtQW8ZOJ//ZC6t0AWcUoKL6QDm/dg5koQalcleRinpB+QadFm894sLbVZ9+N4GVsv1W****==
KeyId

string

Yes

The ID of the key. You can also specify a key alias or a key Amazon Resource Name (ARN). For more information about aliases, see Manage key aliases.

Note

To access a key that belongs to another Alibaba Cloud account, you must specify the key ARN. The key ARN format is acs:kms:${region}:${account}:key/${keyid}.

key-hzz630494463ejqjx****
KeyVersionId

string

Yes

The key version ID. The globally unique identifier of the key version.

2ab1a983-7072-4bbc-a582-584b5bd8****
Algorithm

string

Yes

The decryption algorithm.

RSAES_OAEP_SHA_1
DryRun

string

No

Specifies whether to enable DryRun mode. Valid values:

  • true: Enabled.

  • false (default): Disabled.

DryRun mode is used to test API calls, verify that you have the required permissions on the relevant resources, and check whether the request parameters are configured correctly. When DryRun mode is enabled, KMS always returns a failure with a reason. The failure reasons include the following:

  • DryRunOperationError: The request would succeed if the DryRun parameter were not specified.

  • ValidationError: A parameter specified in the request is invalid.

  • AccessDeniedError: You do not have permission to perform this operation on the KMS resource.

false
Recipient

string

No

{ "AttestationDocument":"base64-encoded-attestion-document", "KeyEncryptionAlgorithm":"RSAES_OAEP_SHA_256" }

Response elements

Element

Type

Description

Example

object

KeyVersionId

string

The version number of the master key used to encrypt the plaintext data.

2ab1a983-7072-4bbc-a582-584b5bd8****
KeyId

string

The key ID. If the KeyId parameter in the request specifies a key alias or key ARN, the key ID is also returned in the response.

key-hzz630494463ejqjx****
RequestId

string

The request ID. This is a unique identifier generated by Alibaba Cloud for the request. You can use this ID to troubleshoot and locate issues.

475f1620-b9d3-4d35-b5c6-3fbdd941423d
Plaintext

string

The decrypted plaintext, encoded in Base64.

SGVsbG8gd29ybGQ=
CiphertextForRecipient

string

***Ciphertext***

Examples

Success response

JSON format

{
  "KeyVersionId": "2ab1a983-7072-4bbc-a582-584b5bd8****",
  "KeyId": "key-hzz630494463ejqjx****",
  "RequestId": "475f1620-b9d3-4d35-b5c6-3fbdd941423d",
  "Plaintext": "SGVsbG8gd29ybGQ=",
  "CiphertextForRecipient": "***Ciphertext***"
}

Error codes

HTTP status code

Error code

Error message

Description
400 Rejected.UnsupportedOperation Unsupported operation. The operation is not supported.
404 Forbidden.AliasNotFound The specified Alias is not found. The error message returned because the specified alias does not exist.
404 Forbidden.KeyNotFound The specified Key is not found. The error message returned because the specified CMK does not exist.

See Error Codes for a complete list.

Release notes

See Release Notes for a complete list.