# IEEE Std 1609.2b-2019 pdf download

IEEE Std 1609.2b-2019 pdf download.IEEE Standard for Wireless Access in Vehicular Environments- Security Services for Applications and Management Messages Amendment 2: PDU Functional Types and Encryption Key Management.

If the key was not “ephemeral”, i.e., generated within the SDS at the time of data encryption, it is referred to as “static”.

Following data encryption, the SDS creates Recipientlnfos which allow the intended recipients to access the data encryption key. Each different key encryption key I will in general correspond to a different intended recipient of the encivpted P[)U.

The recipients are provided information about the data encryption key as follows:

— If the invokingSDEE provided one or more recipient keys, the SDS encrypts the key k with each of those key keys to produce a series of encrypted keys ek1}, with each ek1 an encryption of k with key encryption key I. This process is specified in 5.3.4.3. For each key enc’ption key I, the SDS creates a Recipientinfo structure containing the encrypted key ek1, of the type determined by the type of the recipient’s encryption key as speciFied in 6.3.37. This enables the recipients in possession of the corresponding decryption key to recover the data encryption key.

If the invoking SDEE requested a direct indication of the data encryption key, the SDS creates a single Recipientinfo structure of type PreSharedKeyRecipientlnfo identifying the data encryption key. This enables recipients who already possess the data enction key to idcnti that it is the key to be used to decrypt the encrypted data.

— The SDS then encodes all the Recipientlnfos into a SeguenceOtRecipientlnfo, encodes the SeguenceO fRecipientln fo and the SymmetricCipheext into an EncryptedData, and encapsulates the EncryptedData in an leeel6O9I)ot2Data.

This approach allows an EncryptedData to be created for recipients that already know the data encryption key, for recipients that do not already know the data encryption key, or for a combination of the two types of recipients.

In the Sec-EncryptedData.reguest primitive of 9.3.11.1, the SDEE indicates to the SDS whether to use an ephemeral or static data encryption key by providing or not providing the Data EnclTption Key Type parameter. If the SDEE requested an ephemeral data encryption key, the SI)S may return a cryptomaterial handle (see 4.3.3 and 9.2.2) for that data encryption key in the corresponding Sec-EncryptedData.confirm primitive to enable that data encryption key to be reused if desired.

In the Sec-Encryptedl)ataL)ecryption.confirm primitive of 9.3.13.2, the S1)S may provide a Cryptomaterial Handle for the data encryption key in the Data Encryption Key CMI! parameter. This enables the SDEE that receives this primitive to store the CMH for later use.

5.3.4.2 Data encryption

l)aia encryption is performed as follows:

The plaintext P has the form of a valid encoded Ieee l6O9Doi2Data structure.

A symmetric data encryption key k for an approved symmetric algorithm as specified in 5.3.8 is available as described in 5.3.4.1.

— P is cncitcd with k to obtain a ciphcext C. If the approved symmetric algorithm uses a nonce, that nonce is generated freshly and at random for each new plaintext.

The ciphertext C is encoded as a SymmetricCiphertext.

5.3.4.3 Data encryption key encryption

A data encrypon key can be enç ted for one or more public or symmetric keys resulting in a single encrypted SPDU that may be decrypted by the holder or holders of the decryption key corresponding to any of the encryption keys. Each of the encryption keys used is referred to as a recipient key and the owner of the corresponding decryption key is referred to as a recipient.

Encryption of a data encption key is peorrned as follows:

For each recipient key, the data encryption key k is enciypted with the recipient key to obtain an encrypted data encryption key ek.

If the recipient key is an asymmetric public key, the cryptographic processing for encryption with the public key varies depending on the source of the public key; see 5.3.5 for details.

— If the recipient key is a symmetric key, the data encryption key is encrypted with the symmetric key as specified in 5.3.8 and the relevant Recipientinfo is of type SymmRecipientlnfo.