New illustrations for ECDSA and Schnorr signatures

schnorr.asciidoc

@@ -29,6 +29,13 @@ In Bitcoin, Schnorr signatures are applied to the secp256k1 elliptic curve. This
 
 The BIP-340 document contains more than simply the final implementation of Bitcoin's Schnorr signatures: it describes the various design decisions and the rationale for the choices that were made. While we won't repeat those explanations here, we urge you to read BIP-340 for yourself, so that you may better understand the process and reasoning behind the specification.
 
+Illustration footnote:[The Schnorr signature illustration is sourced from Stepan Snigirev's article "How Schnorr Signatures May Improve Bitcoin" (https://medium.com/cryptoadvance/how-schnorr-signatures-may-improve-bitcoin-91655bcb4744)]
+
+[[schnorr_sigs_illustrated]]
+.Schnorr signatures illustrated
+image::images/schnorr_signatures.png["Schnorr signatures illustrated"]
+
+
 ==== Creting a Schnorr signature
 
 The first part of a signature scheme is the formula used to create the digital signature, which is shown in <<schnorr_signing_formula>>: