Root & Leaf

Digest From Leaf And Share

The digest is recomputed from the leaf id and server share.

highlighted = computed this step

Make a small check value

The toy digest is the leaf id plus the server share, reduced modulo the root modulus.

digest=(leaf+share) mod n\text{digest}=(\text{leaf}+\text{share})\bmod n
Digest from leaf and shareThe toy root-to-leaf chain is recomputed from the signed digest.Digest from leaf and share - root verifies leafToy Root CAn=55, e=3Leaf cert binds share 19digest=33, sig=22

Add the two bound values

Leaf id 14 plus server share 19 gives the digest input.

14+1914+19
Digest from leaf and shareThe toy root-to-leaf chain is recomputed from the signed digest.Digest from leaf and share - root verifies leafToy Root CAn=55, e=3Leaf cert binds share 19digest=33, sig=22

Reduce under the root modulus

Modulo n=55, the digest is 33.

(14+19) mod 55=33(14+19)\bmod{}55=33
Digest from leaf and shareThe toy root-to-leaf chain is recomputed from the signed digest.Digest from leaf and share - root verifies leafToy Root CAn=55, e=3Leaf cert binds share 19digest=33, sig=22

Summary

The digest is derived from the leaf and share; it is not accepted from prose.

digest=33\text{digest}=33
Digest from leaf and shareThe toy root-to-leaf chain is recomputed from the signed digest.Digest from leaf and share - root verifies leafToy Root CAn=55, e=3Leaf cert binds share 19digest=33, sig=22