Decrypt

Available in Classic and VPC

Decrypt the ciphertext encrypted with a key. It can only be requested as an AES256 or RSA2048 key type.

Caution

The data encrypted with the master key and returned consists of KMS prefix + ciphertext. The KMS prefix is composed of ncpkms:version information, and it must be specified exactly with the ciphertext because it will be decrypted with the key version specified in the decryption request. If the KMS prefix is incorrect, it will not be decrypted correctly, so be sure to manage the encryption in the form it is returned, with no arbitrary removals or manipulations.

ncpkms:v1:XjsPWPjqPrBi1N2DupSiSbX/ATkGmKA
---------- -------------------------------
KMS prefix        ciphertext

Request

This section describes the request format. The method and URI are as follows:

Method	URI
POST	/kms/v1/keys/{keyTag}/decrypt

Request headers

For information about the request headers common to all Key Management Service APIs, see the token authentication method in Key Management Service request headers.

Request path parameters

You can use the following path parameters with your request:

Field	Type	Required	Description
`keyTag`	String	Required	Key tag Unique identifier for the key derived from the key name. See Get key list. Use to request encryption or decryption with REST APIs. Key tags are not treated as confidential information.

Request body

You can include the following data in the body of your request:

Field	Type	Required	Description
`ciphertext`	String or Array[String]	Required	String created by encrypting a plaintext
`context`	String	Conditional	Base64-encoded string data The `context` parameter value used when encrypting data with a key that has convergent encryption applied is required.

Request example

The request example is as follows:

Request ciphertext as String type

curl --location --request POST 'https://ocapi.ncloud.com/kms/v1/keys/a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0u1v2w3x4y5z6/decrypt' \
--header 'x-ncp-ocapi-token: {Access Token}' \
--data '{
  "ciphertext": "{CIPHERTEXT}",
  "context": "{BASE64_CONTEXT}"
}'

Request ciphertext as Array[String] type

curl --location --request POST 'https://ocapi.ncloud.com/kms/v1/keys/a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0u1v2w3x4y5z6/decrypt' \
--header 'x-ncp-ocapi-token: {Access Token}' \
--data '{
  "ciphertext": ["{CIPHERTEXT_1}", "{CIPHERTEXT_2}", "{CIPHERTEXT_3}"],
  "context": "{BASE64_CONTEXT}"
}'

Response

This section describes the response format.

Response body

The response body includes the following data:

Field	Type	Required	Description
`code`	String	-	Success or Failure
`data`	Object	-	Response result
`data.plaintext`	String or Array[String]	-	Decrypted string data Base64-encoded string data before encryption

Response status codes

For information about the response status codes common to all Key Management Service APIs, see Key Management Service response status codes.

Response example

The response example is as follows:

Request ciphertext as String type

{
    "code": "SUCCESS",
    "data": {
        "plaintext": "{BASE64_PLAINTEXT}"
    }
}

Request ciphertext as Array[String] type

{
    "code": "SUCCESS",
    "data": {
        "plaintext": [
            "{BASE64_PLAINTEXT_1}",
            "{BASE64_PLAINTEXT_2}",
            "{BASE64_PLAINTEXT_3}"
        ]
    }
}

Decrypt data encrypted with RSA2048 public key

For RSA2048, even data encrypted directly with a public key without calling the NCP KMS API can be decrypted using this API, provided it was encrypted under the same conditions specified in Encrypt.

When requesting decryption, you must Base64-encode the RSA ciphertext, append the KMS ciphertext identifier prefix, and pass it as ciphertext.

ncpkms:v{key version}:{Base64 (RSA ciphertext)}

For public key query and encryption examples, see Get public key.

Note

Since KMS decrypts the data using the same parameters used for encryption, there is no need to specify separate algorithm parameters. If you want to decrypt data that was encrypted directly with the public key, you must match the parameters exactly. For more information, see the encryption parameters in Encrypt.