Verify the Chain

Signature Opens Under Root

The root public key opens the toy signature to the recomputed digest.

highlighted = computed this step

Open the signature with the root key

The verifier raises the signature to the root public exponent modulo the root modulus.

verify se mod n\text{verify }s^e\bmod n
Open the signatureThe toy RSA signature check is recomputed from signature, exponent, and modulus.Open the signature - 22^3 mod 55stepbitpriorsquaremultiplyresult011122221122443333

Use the pinned signature

The toy signature is 22, and the root exponent is 3.

22322^3
Open the signatureThe toy RSA signature check is recomputed from signature, exponent, and modulus.Open the signature - 22^3 mod 55stepbitpriorsquaremultiplyresult011122221122443333

It opens to the digest

Modulo n=55, the signature opens to 33.

223 mod 55=3322^3\bmod{}55=33
Open the signatureThe toy RSA signature check is recomputed from signature, exponent, and modulus.Open the signature - 22^3 mod 55stepbitpriorsquaremultiplyresult011122221122443333

Summary

The opened signature matches the recomputed digest.

opened digest=33\text{opened digest}=33
Open the signatureThe toy RSA signature check is recomputed from signature, exponent, and modulus.Open the signature - 22^3 mod 55stepbitpriorsquaremultiplyresult011122221122443333