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Decrypt

Specification¶

This operation requests the server to perform a decryption operation on the provided data using a Managed Cryptographic Object as the key for the decryption operation.

The request contains information about the cryptographic parameters (mode and padding method), the data to be decrypted, and the IV/Counter/Nonce to use. The cryptographic parameters MAY be omitted from the request as they can be specified as associated attributes of the Managed Cryptographic Object. The initialization vector/counter/nonce MAY also be omitted from the request if the algorithm does not use an IV/Counter/Nonce.

The response contains the Unique Identifier of the Managed Cryptographic Object used as the key and the result of the decryption operation.

The success or failure of the operation is indicated by the Result Status (and if failure, the Result Reason) in the response header.

Implementation¶

To see the list of supported cryptographic algorithms, please refer to Supported Algorithms.

Example - AES GCM decryption¶

Decrypting the text Hello, world! with symmetric key 027cced1-ff2b-4bd3-a200-db1041583bd (go to Create to see how to create the symmetric key).

Instead of using the UID of the key, we can use the unique tag of the key MySymmetricKey. The key must be uniquely identified. It is possible to use multiple tags to identify a key; for instance symmetric keys automatically get a system tag _kk. See tagging for more information on tags.

Corresponding Cosmian CLI command:

cosmian kms sym decrypt /tmp/encrypted.bin -t MySymmetricKey

where /tmp/encrypted.bin contains the a concatenation of the the nonce, the encrypted and the authentication tag in that order.

The JSON TTLV request the same information as in the Encrypt Response:

the encrypted data
the nonce: 12 bytes
the authentication tag: 16 bytes

RequestResponse

    {
      "tag": "Decrypt",
      "type": "Structure",
      "value": [
        {
          "tag": "UniqueIdentifier",
          "type": "TextString",
          "value": "[\"MySymmetricKey\"]"
        },
        {
          "tag": "Data",
          "type": "ByteString",
          "value": "40D59A0735811135749A507FDEB3"
        },
        {
          "tag": "IvCounterNonce",
          "type": "ByteString",
          "value": "DBDD622A64F7D65E75894B1B"
        },
        {
          "tag": "AuthenticatedEncryptionTag",
          "type": "ByteString",
          "value": "50FCE680540BD3E96EFA9218A2F1009D"
        }
      ]
    }

    {
      "tag": "DecryptResponse",
      "type": "Structure",
      "value": [
        {
          "tag": "UniqueIdentifier",
          "type": "TextString",
          "value": "027cced1-ff2b-4bd3-a200-db1041583bdc"
        },
        {
          "tag": "Data",
          "type": "ByteString",
          // Hello, world! as UTF-8 bytes in hex
          "value": "48656C6C6F2C20776F726C64210A"
        }
      ]
    }

Example - Covercrypt¶

Decrypting the text Hello, world! with Covercrypt user decryption key df871e79-0923-47cd-9078-bbec83287c85 (go to Create to see how to create the Covercrypt user decryption key).

Instead of using the UID of the key, we can use the unique tag of the key MyUserKey. The key must be uniquely identified. It is possible to use multiple tags to identify a key; for instance Covercrypt user decryption keys automatically get a system tag _uk. See tagging for more information on tags.

Corresponding Cosmian CLI command:

cosmian kms cc decrypt /tmp/encrypted.bin  -t MyUserKey

RequestResponse

    {
      "tag": "Decrypt",
      "type": "Structure",
      "value": [
        {
          "tag": "UniqueIdentifier",
          "type": "TextString",
          "value": "[\"MyUserKey\"]"
        },
        {
          "tag": "CryptographicParameters",
          "type": "Structure",
          "value": [
            {
              "tag": "CryptographicAlgorithm",
              "type": "Enumeration",
              "value": "CoverCrypt"
            }
          ]
        },
        {
          "tag": "Data",
          "type": "ByteString",
          "value": "AEA6CF824612448B8445CAF46F9D987161706DAD6E43DFD1A57DD0F39869DC39A68096657A3EDC03CBC619D563744D2CC9819B6A9AB9A3893FD27F452F49A244A8CAA42279C4705D4D3A9E04D2B7887F0100D947F27D27BBD1D06F5A65087F73B8AAB617568761273282D4C14770FFCBA47200D02DDB4C48E1028DC5C50DE860A10A26E35AC405EFE6405486B56E9968594471075687D7BF6935BD003D"
        }
      ]
    }

    {
      "tag": "DecryptResponse",
      "type": "Structure",
      "value": [
        {
          "tag": "UniqueIdentifier",
          "type": "TextString",
          "value": "df871e79-0923-47cd-9078-bbec83287c85"
        },
        {
          "tag": "Data",
          "type": "ByteString",
          // Hello, world! as UTF-8 bytes in hex
          "value": "0048656C6C6F2C20776F726C64210A"
        }
      ]
    }