The Finished check starts with a transcript hash. This lesson pins the toy hash inputs and output.
Why hash the transcript
Finished does not check one message in isolation. It checks a transcript hash built from the ordered toy values.
hash the ordered transcript \text{hash the ordered transcript} hash the ordered transcript Toy transcript hash Toy TLS transcript table recomputed from DH and RSA pins. Toy transcript hash - hash=43 item value check ClientHello 4 pinned ServerHello 9 pinned Certificate digest 33 root signature ServerKeyShare 19 DH public ClientKeyShare 8 DH public Transcript hash 43 weighted mod 97 Shared secret 2 DH recompute Client Finished 64 toy check Server Finished 70 toy check
Pin the hashed values
The toy hash uses hello values 4 and 9, certificate digest 33, server share 19, and client share 8.
values feed hash \text{values feed hash} values feed hash Toy transcript hash Toy TLS transcript table recomputed from DH and RSA pins. Toy transcript hash - hash=43 item value check ClientHello 4 pinned ServerHello 9 pinned Certificate digest 33 root signature ServerKeyShare 19 DH public ClientKeyShare 8 DH public Transcript hash 43 weighted mod 97 Shared secret 2 DH recompute Client Finished 64 toy check Server Finished 70 toy check
Read the toy hash
Weighted reduction modulo 97 gives transcript hash 43.
H = 43 ( m o d 97 ) H=43\pmod{97} H = 43 ( mod 97 ) Toy transcript hash Toy TLS transcript table recomputed from DH and RSA pins. Toy transcript hash - hash=43 item value check ClientHello 4 pinned ServerHello 9 pinned Certificate digest 33 root signature ServerKeyShare 19 DH public ClientKeyShare 8 DH public Transcript hash 43 weighted mod 97 Shared secret 2 DH recompute Client Finished 64 toy check Server Finished 70 toy check
Summary
The transcript hash commits to order and values before Finished. NOTE: toy-modulus; no-padding; no-side-channel; no-production; never-roll-your-own. Toy transcript only: not real TLS bytes, not real certificate validation, no AEAD record protection, and no security-size claims.
hash recomputed \text{hash recomputed} hash recomputed Toy transcript hash Toy TLS transcript table recomputed from DH and RSA pins. Toy transcript hash - hash=43 item value check ClientHello 4 pinned ServerHello 9 pinned Certificate digest 33 root signature ServerKeyShare 19 DH public ClientKeyShare 8 DH public Transcript hash 43 weighted mod 97 Shared secret 2 DH recompute Client Finished 64 toy check Server Finished 70 toy check