Secure AuthenticationのトピックRe: A71CH ConstructedSecret Question

A71CH ConstructedSecret Question

michael_d_adams — Wed, 01 Dec 2021 18:23:41 GMT

Section 6.2.2.1 "ConstructedSecret" of AN12229 "APDU Specification of A71CH Security Module Rev. 3.0" describes a method for creating longer secrets from the 8 available 128bit symmetric keys available in the part. It indicates that the Constructed Secret is formed from two nibbles of a byte where the upper nibble is the number of 128bit symmetric keys to be used and the lower nibble is the starting index.

If we choose the lower nibble to be 0x7 meaning symmetric key #8 and we select the upper nibble to be 0x3 meaning three 128bit keys, would the keys wrap so that they are #8, #1, & #2?

Re: A71CH ConstructedSecret Question

Kan_Li — Thu, 02 Dec 2021 06:20:40 GMT

Hi @michael_d_adams ,

No, such kind of wrap feature is not supported.

Have a great day,
Kan

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