Chapter 5 Figure 5-10 Correction

[traffictse]

The current Figure 5-10 titled "Extending a parent public key to create a child public key" is quoted as:

This previous figure (not the current one) intended to show the two ways to derive a child public key: 1) from the child private key derived from the parent private key by CKDprv; 2) directly from the parent public key by CKDpub. And the current one plans to show the way 2) only.

However, in the previous figure, it was inappropriate that an arrow was drawn from Parent Private Key directly to Child Private Key without HMAC-SHA512 involved in the middle.

Also, in the current figure, it is inappropriate that an arrow is drawn from Parent Public Key directly to Child Public Key bypassing the middle HMAC-SHA512, which seems impossible. The arrow from Child Public Key to Child Chain Code also does not exist.

The following is for reference only to show both ways of the deviation of a child public key.

[RequestPrivacy]

However, in the previous figure, it was inappropriate that an arrow was drawn from Parent Private Key directly to Child Private Key without HMAC-SHA512 involved in the middle.

Also, in the current figure, it is inappropriate that an arrow is drawn from Parent Public Key directly to Child Public Key bypassing the middle HMAC-SHA512, which seems impossible.

See my explanation of the "bypassing" of HMAC-SHA512 by the parent public/private key in your issue #1023. The same applies here.

The arrow from Child Public Key to Child Chain Code also does not exist.

I think that's correct, the child chain code should be the same (the right 256 bits of the HMAC-SHA512) and don't depend on the child public key in any form.