kms_re_encrypt: Decrypts ciphertext and then reencrypts it entirely within...

Description Usage Arguments Details Request syntax Examples

View source: R/kms_operations.R

Description

Decrypts ciphertext and then reencrypts it entirely within AWS KMS. You can use this operation to change the customer master key (CMK) under which data is encrypted, such as when you manually rotate a CMK or change the CMK that protects a ciphertext. You can also use it to reencrypt ciphertext under the same CMK, such as to change the encryption context of a ciphertext.

Usage

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kms_re_encrypt(CiphertextBlob, SourceEncryptionContext, SourceKeyId,
  DestinationKeyId, DestinationEncryptionContext,
  SourceEncryptionAlgorithm, DestinationEncryptionAlgorithm, GrantTokens)

Arguments

CiphertextBlob

[required] Ciphertext of the data to reencrypt.

SourceEncryptionContext

Specifies the encryption context to use to decrypt the ciphertext. Enter the same encryption context that was used to encrypt the ciphertext.

An encryption context is a collection of non-secret key-value pairs that represents additional authenticated data. When you use an encryption context to encrypt data, you must specify the same (an exact case-sensitive match) encryption context to decrypt the data. An encryption context is optional when encrypting with a symmetric CMK, but it is highly recommended.

For more information, see Encryption Context in the AWS Key Management Service Developer Guide.

SourceKeyId

A unique identifier for the CMK that is used to decrypt the ciphertext before it reencrypts it using the destination CMK.

This parameter is required only when the ciphertext was encrypted under an asymmetric CMK. Otherwise, AWS KMS uses the metadata that it adds to the ciphertext blob to determine which CMK was used to encrypt the ciphertext. However, you can use this parameter to ensure that a particular CMK (of any kind) is used to decrypt the ciphertext before it is reencrypted.

If you specify a KeyId value, the decrypt part of the ReEncrypt operation succeeds only if the specified CMK was used to encrypt the ciphertext.

To specify a CMK, use its key ID, Amazon Resource Name (ARN), alias name, or alias ARN. When using an alias name, prefix it with "alias/".

For example:

  • Key ID: 1234abcd-12ab-34cd-56ef-1234567890ab

  • Key ARN: arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab

  • Alias name: alias/ExampleAlias

  • Alias ARN: arn:aws:kms:us-east-2:111122223333:alias/ExampleAlias

To get the key ID and key ARN for a CMK, use ListKeys or DescribeKey. To get the alias name and alias ARN, use ListAliases.

DestinationKeyId

[required] A unique identifier for the CMK that is used to reencrypt the data. Specify a symmetric or asymmetric CMK with a KeyUsage value of ENCRYPT_DECRYPT. To find the KeyUsage value of a CMK, use the DescribeKey operation.

To specify a CMK, use its key ID, Amazon Resource Name (ARN), alias name, or alias ARN. When using an alias name, prefix it with "alias/". To specify a CMK in a different AWS account, you must use the key ARN or alias ARN.

For example:

  • Key ID: 1234abcd-12ab-34cd-56ef-1234567890ab

  • Key ARN: arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab

  • Alias name: alias/ExampleAlias

  • Alias ARN: arn:aws:kms:us-east-2:111122223333:alias/ExampleAlias

To get the key ID and key ARN for a CMK, use ListKeys or DescribeKey. To get the alias name and alias ARN, use ListAliases.

DestinationEncryptionContext

Specifies that encryption context to use when the reencrypting the data.

A destination encryption context is valid only when the destination CMK is a symmetric CMK. The standard ciphertext format for asymmetric CMKs does not include fields for metadata.

An encryption context is a collection of non-secret key-value pairs that represents additional authenticated data. When you use an encryption context to encrypt data, you must specify the same (an exact case-sensitive match) encryption context to decrypt the data. An encryption context is optional when encrypting with a symmetric CMK, but it is highly recommended.

For more information, see Encryption Context in the AWS Key Management Service Developer Guide.

SourceEncryptionAlgorithm

Specifies the encryption algorithm that AWS KMS will use to decrypt the ciphertext before it is reencrypted. The default value, SYMMETRIC_DEFAULT, represents the algorithm used for symmetric CMKs.

Specify the same algorithm that was used to encrypt the ciphertext. If you specify a different algorithm, the decrypt attempt fails.

This parameter is required only when the ciphertext was encrypted under an asymmetric CMK.

DestinationEncryptionAlgorithm

Specifies the encryption algorithm that AWS KMS will use to reecrypt the data after it has decrypted it. The default value, SYMMETRIC_DEFAULT, represents the encryption algorithm used for symmetric CMKs.

This parameter is required only when the destination CMK is an asymmetric CMK.

GrantTokens

A list of grant tokens.

For more information, see Grant Tokens in the AWS Key Management Service Developer Guide.

Details

The ReEncrypt operation can decrypt ciphertext that was encrypted by using an AWS KMS CMK in an AWS KMS operation, such as Encrypt or GenerateDataKey. It can also decrypt ciphertext that was encrypted by using the public key of an asymmetric CMK outside of AWS KMS. However, it cannot decrypt ciphertext produced by other libraries, such as the AWS Encryption SDK or Amazon S3 client-side encryption. These libraries return a ciphertext format that is incompatible with AWS KMS.

When you use the ReEncrypt operation, you need to provide information for the decrypt operation and the subsequent encrypt operation.

Unlike other AWS KMS API operations, ReEncrypt callers must have two permissions:

To permit reencryption from

or to a CMK, include the "kms:ReEncrypt*" permission in your key policy. This permission is automatically included in the key policy when you use the console to create a CMK. But you must include it manually when you create a CMK programmatically or when you use the PutKeyPolicy operation set a key policy.

The CMK that you use for this operation must be in a compatible key state. For details, see How Key State Affects Use of a Customer Master Key in the AWS Key Management Service Developer Guide.

Request syntax

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svc$re_encrypt(
  CiphertextBlob = raw,
  SourceEncryptionContext = list(
    "string"
  ),
  SourceKeyId = "string",
  DestinationKeyId = "string",
  DestinationEncryptionContext = list(
    "string"
  ),
  SourceEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256",
  DestinationEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256",
  GrantTokens = list(
    "string"
  )
)

Examples

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# The following example reencrypts data with the specified CMK.
svc$re_encrypt(
  CiphertextBlob = "<binary data>",
  DestinationKeyId = "0987dcba-09fe-87dc-65ba-ab0987654321"
)

paws.security.identity documentation built on Jan. 14, 2020, 5:08 p.m.