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.
The re_encrypt operation can decrypt ciphertext that
was encrypted by using an AWS KMS CMK in an AWS KMS operation, such as
encrypt or
generate_data_key. 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 re_encrypt operation, you need to
provide information for the decrypt operation and the subsequent encrypt
operation.
If your ciphertext was encrypted under an asymmetric CMK, you must
use the SourceKeyId parameter to identify the CMK that encrypted
the ciphertext. You must also supply the encryption algorithm that
was used. This information is required to decrypt the data.
If your ciphertext was encrypted under a symmetric CMK, the
SourceKeyId parameter is optional. AWS KMS can get this
information from metadata that it adds to the symmetric ciphertext
blob. This feature adds durability to your implementation by
ensuring that authorized users can decrypt ciphertext decades after
it was encrypted, even if they've lost track of the CMK ID. However,
specifying the source CMK is always recommended as a best practice.
When you use the SourceKeyId parameter to specify a CMK, AWS KMS
uses only the CMK you specify. If the ciphertext was encrypted under
a different CMK, the re_encrypt operation fails.
This practice ensures that you use the CMK that you intend.
To reencrypt the data, you must use the DestinationKeyId parameter
specify the CMK that re-encrypts the data after it is decrypted. You
can select a symmetric or asymmetric CMK. If the destination CMK is
an asymmetric CMK, you must also provide the encryption algorithm.
The algorithm that you choose must be compatible with the CMK.
When you use an asymmetric CMK to encrypt or reencrypt data, be sure to record the CMK and encryption algorithm that you choose. You will be required to provide the same CMK and encryption algorithm when you decrypt the data. If the CMK and algorithm do not match the values used to encrypt the data, the decrypt operation fails.
You are not required to supply the CMK ID and encryption algorithm when you decrypt with symmetric CMKs because AWS KMS stores this information in the ciphertext blob. AWS KMS cannot store metadata in ciphertext generated with asymmetric keys. The standard format for asymmetric key ciphertext does not include configurable fields.
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.
Cross-account use: Yes. The source CMK and destination CMK can be in different AWS accounts. Either or both CMKs can be in a different account than the caller.
Required permissions:
kms:ReEncryptFrom permission on the source CMK (key policy)
kms:ReEncryptTo permission on the destination CMK (key policy)
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
put_key_policy operation to set a key policy.
Related operations:
decrypt
encrypt
generate_data_key
generate_data_key_pair
kms_re_encrypt(CiphertextBlob, SourceEncryptionContext, SourceKeyId,
DestinationKeyId, DestinationEncryptionContext,
SourceEncryptionAlgorithm, DestinationEncryptionAlgorithm, GrantTokens)A list with the following syntax:
list(
CiphertextBlob = raw,
SourceKeyId = "string",
KeyId = "string",
SourceEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256",
DestinationEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256"
)
[required] Ciphertext of the data to reencrypt.
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.
Specifies the customer master key (CMK) that AWS KMS will use to decrypt the ciphertext before it is re-encrypted. Enter a key ID of the CMK that was used to encrypt the ciphertext.
This parameter is required only when the ciphertext was encrypted under an asymmetric CMK. If you used a symmetric CMK, AWS KMS can get the CMK from metadata that it adds to the symmetric ciphertext blob. However, it is always recommended as a best practice. This practice ensures that you use the CMK that you intend.
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
list_keys or describe_key. To
get the alias name and alias ARN, use
list_aliases.
[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
describe_key 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
list_keys or describe_key. To
get the alias name and alias ARN, use
list_aliases.
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.
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.
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.
A list of grant tokens.
For more information, see Grant Tokens in the AWS Key Management Service Developer Guide.
svc$re_encrypt(
CiphertextBlob = raw,
SourceEncryptionContext = list(
"string"
),
SourceKeyId = "string",
DestinationKeyId = "string",
DestinationEncryptionContext = list(
"string"
),
SourceEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256",
DestinationEncryptionAlgorithm = "SYMMETRIC_DEFAULT"|"RSAES_OAEP_SHA_1"|"RSAES_OAEP_SHA_256",
GrantTokens = list(
"string"
)
)
if (FALSE) {
# The following example reencrypts data with the specified CMK.
svc$re_encrypt(
CiphertextBlob = "",
DestinationKeyId = "0987dcba-09fe-87dc-65ba-ab0987654321"
)
}
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