TL;DR: The coming Bitcoin Cash (BCH) hard fork, a network software upgrade scheduled for 15 May 2019, brings with it beginnings of an innovation Bitcoin Core (BTC) developers have considered for more than a decade, Schnorr Signatures. The idea applied to cryptocurrency has been an off-and-on discussion since at least 2009 for BTC, and the concept itself is thirty years old. Under the guidance of independent developer Mark B. Lundeberg, BCH begins its Schnorr Signatures journey in a matter of days.
Bitcoin Cash Begins its Schnorr Signatures Journey
What would become Schnorr Signatures were presented summer of 1989 in Santa Barbara, California to the International Association for Cryptologic Research at its Conference on the Theory and Application of Cryptology (known as Crypto, but no relation to cryptocurrency as we might use the term today). In total, 60 papers were discussed, a particularly fruitful year for the conference — it would take nearly a quarter century to match that number and eventually best it.
Among that year’s presentations was Efficient Identification and Signatures for Smart Cards by C.P. Schnorr, Universitdt Frankfurt. The typographical glyph, section sign (§), rested on the title’s final s, referring readers to an historic footnote: a European patent application was filed on the discovery’s behalf, and would lock Schnorr Signatures away for two decades from the open source development community as a result. U.S. Patent 4,995,082 only technically expires this year forever on the 10th of May. But it would be hard to argue with the academic’s rush to protect his work. Credit cards were to become ubiquitous, and any invention making their use easier was something giant companies would seize on and quickly block him from if he didn’t get there first.
Seize they did. Assignees Xerox Corporation, United States Department of Energy, Sun Microsystems, Inc., Pitney Bowes Inc. are a just a sampling of those who showed interest in Schnorr’s ideas. Claus-Peter Schnorr proposed a more efficient method for gathering digital signatures. Picking up from the work of a handful of others, Schnorr proposed “an efficient algorithm to preprocess the exponentiation of random numbers. This preprocessing makes signature generation very fast. It also improves the efficiency of the other discrete log-cryptosystems. The preprocessing algorithm is based on two fundamental principles local randomization and internal randomization,” he explained.
Precise, Linear, Understated
His work went on to help the smart card industry bloom. In 2013, he was honored, along with Jean-Jacques Quisquater, with the RSA Excellence in the Field of Mathematics Award. “Professor Jean-Jacques Quisquater and Dr. Claus Schnorr have both contributed pioneering work in efficient zero-knowledge authentication schemes. The GQ and Schnorr identification and signature schemes represent a seminal translation of cryptographic theory into practice. Their work has had a major impact on the early development of the smartcard industry,” the award inscription read.
The company named after its founders, Ron Rivest, Adi Shamir, Leonard Adleman, is well known in the worlds of computer and network security (RSA public key cryptography algorithm). Its annual conference is something of appointment attendance for those in the know, and is held at the Moscone Center in San Francisco. In what appears to be a rare publicly documented appearance, Schnorr ascends the stage behind Quisquater, who is by comparison seemingly frazzled and a tad disheveled … which extends to his acceptance speech.
Schnorr is immediately in personal contrast: tidy, precise in his language, linear, understated. These are apt descriptions of Schnorr Signatures as well, it turns out. There’s widespread belief Satoshi Nakamoto avoided use of Schnorr due to patent liabilities, and instead opted for a generic variation on its theme, Elliptic Curve Digital Signature Algorithm (ECDSA). It has worked fine, but lacks what developer Mark B. Lundeberg calls “linearity,” as Schnorr solves some of ECDSA’s clunkier features.
A Simple Change
“In the end, it’s a simple change,” Lundeberg explained of Bitcoin Cash’s pending upgrade for 15 May 2019, “add some the mathematical code that lets you verify Schnorr signatures, which is straight-forward compared to [ECDSA] (Amaury Séchet had this code ready to go); then, upgrade the opcodes (like OP_CHECKSIG) to optionally accept Schnorr signatures in place of ECDSA. That’s it.”
Why, then, hasn’t BTC implemented the coveted advantage, which they’ve acknowledged for ten years, of Schnorr? “Such a simple thing cannot be done on BTC,” Lundeberg insisted. “With the restriction to soft forks, one cannot be so direct. To make things worse, you cannot just think about upgrading one feature at a time.” Schnorr Signatures also have been packaged with other software by BTC devs, such as Taproot, and the incentive to make one giant change at once, not to mention BTC devs’ penchant for paralysis by analysis, has retarded progress in this regard.
And like its namesake, the upgrade to BCH is not being hyped by developers, and is in fact being understated on purpose, calling the 15 May 2019 Schnorr involvement the “most-basic” of their variety. The hope is other features will come onto BCH as need permits. They “are just a hard fork away,” Lundeberg notes. “We don’t need to hold back that very basic first step, waiting until all the more complex elaborations have been perfectly engineered.”
DISCLOSURE: The author holds cryptocurrency as part of his financial portfolio, including BCH.
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