2.2.1 Client NTP Request

The subfields of the Authenticator field of the Client NTP Request message include the following.


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Key Identifier

Crypto-Checksum (16 bytes)

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Key Identifier (4 bytes): A 32-bit unsigned integer in little-endian byte order (least significant byte first). This field identifies the cryptographic key used to generate the crypto-checksum. The least significant 31 bits are the least significant 31 bits of a relative identifier (RID) for a trusted account, as described in section 3.1.3. The most significant bit of the key identifier is a 1-bit key selector that identifies the cryptographic key to use in the pair of keys associated with the account. For more information on the semantics of this key selector, see sections 3.1.5, 3.1.6, and 3.2.5.

Crypto-Checksum (16 bytes): A 128-bit crypto-checksum that the encryption procedure computes. For more information, see section 3.2.5.<3>