rfc7298v3.txt | rfc7298.txt | |||
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Many practical applications of HMAC for authentication of datagram- | Many practical applications of HMAC for authentication of datagram- | |||
based network protocols (including routing protocols) involve the | based network protocols (including routing protocols) involve the | |||
padding procedure, a design-specific conditioning of the message that | padding procedure, a design-specific conditioning of the message that | |||
both the sender and the receiver perform before the HMAC computation. | both the sender and the receiver perform before the HMAC computation. | |||
The specific padding procedure of this mechanism addresses the | The specific padding procedure of this mechanism addresses the | |||
following needs: | following needs: | |||
o Data Initialization | o Data Initialization | |||
A design that places the HMAC result(s) computed for a message | A design that places the HMAC result(s) computed for a message | |||
inside the same message after the computation has to allocate in | inside that same message after the computation has to have | |||
the message some data unit(s) purposed for the result(s) (in this | previously (i.e., before the computation) allocated in that | |||
mechanism, it is the HMAC TLV(s); see Section 4.3). The padding | message some data unit(s) purposed specifically for those HMAC | |||
procedure sets the respective octets of the data unit(s), in the | result(s) (in this mechanism, it is the HMAC TLV(s); see | |||
simplest case to a fixed value known as the padding constant. | Section 4.3). The padding procedure sets the respective octets of | |||
the data unit(s), in the simplest case to a fixed value known as | ||||
the padding constant. | ||||
The particular value of the constant is specific to each design. | The particular value of the constant is specific to each design. | |||
For instance, in [RIP2-AUTH] as well as works derived from it | For instance, in [RIP2-AUTH] as well as works derived from it | |||
([ISIS-AUTH-B], [OSPF2-AUTH], and [OSPF3-AUTH-BIS]), the value is | ([ISIS-AUTH-B], [OSPF2-AUTH], and [OSPF3-AUTH-BIS]), the value is | |||
0x878FE1F3. In many other designs (for instance, [RFC3315], | 0x878FE1F3. In many other designs (for instance, [RFC3315], | |||
[RFC3931], [RFC4030], [RFC4302], [RFC5176], and [ISIS-AUTH-A]), | [RFC3931], [RFC4030], [RFC4302], [RFC5176], and [ISIS-AUTH-A]), | |||
the value is 0x00. | the value is 0x00. | |||
However, the HMAC construction is defined on the basis of a | However, the HMAC construction is defined on the basis of a | |||
cryptographic hash algorithm, that is, an algorithm meeting a | cryptographic hash algorithm, that is, an algorithm meeting a | |||
particular set of requirements made for any input message. Thus, | particular set of requirements made for any input message. Thus, | |||
any padding constant values, whether single- or multiple-octet, as | any padding constant values, whether single- or multiple-octet, as | |||
well as any other message-conditioning methods, don't affect | well as any other message-conditioning methods, don't affect | |||
cryptographic characteristics of the hash algorithm and the HMAC | cryptographic characteristics of the hash algorithm and the HMAC | |||
construction, respectively. | construction, respectively. | |||
End of changes. 2 change blocks. | ||||
6 lines changed or deleted | 7 lines changed or added | |||
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