Renato Schiavinato Lopez
Renato Schiavinato Lopez builds security processes for the inconvenient moments: when software is gone, the instructions are old, the people involved are stressed, and the person who designed the system is not there.
He is the founder of GRIFORTIS and the creator of DuraShare, an open protocol for splitting and recovering Bitcoin BIP39 backups with threshold cryptography, offline tools, paper artifacts, and a manual fallback. His question is not merely whether a backup is cryptographically sound, but whether ordinary people can operate it years later without turning recovery into a leap of faith.
He also created SeReCoLiPrInGo—a framework for treating self-custody as seven competing concerns: Security, Resilience, Coercion, Liquidity, Privacy, Inheritance, and Governance. It is an argument against the idea that a hardware wallet, a seed phrase, or multisig alone can solve custody.
Before moving into Bitcoin self-custody, Renato was an Agile Coach. He designed and facilitated hundreds of workshops, trainings, and working sessions in Portuguese and English—getting groups to make decisions, surface assumptions, build shared understanding, and leave with a process they could actually use. That background now shapes his security work: DuraShare treats custody as a human coordination problem as much as a cryptographic one.
In 2026, he brought DuraShare to TABConf, UFMG, Casa21, and Brazilian BitDevs—not as a product pitch, but as something participants could calculate, audit, and recover themselves.
GRIFORTIS
Session
TL;DR: Picture this: on an air-gapped device, you create a 3-of-5 backup of your BIP39 seed. Years later, you recover it using just pen, paper and a calculator. This is one of the many cool things DuraShare can do. In this hands-on workshop, you’ll see a live air-gapped ceremony in action, perform an individual share audit, and manually reconstruct a toy model seed (3 words plus checksum) step-by-step to experience true software-independent recovery firsthand.
Abstract
Long-horizon cryptocurrency self-custody faces a dual failure model: exposing or losing a master BIP39 mnemonic, or surviving decades only to find recovery software, operating systems, or specialized hardware obsolete or unavailable. Existing approaches may use custom share encodings, alternative wallet-derivation models, or high manual friction.
This workshop presents DuraShare, a BIP39-native k-of-n threshold backup with full manual fallback and per-share audit capability. For everyday convenience we adopt a software-assisted model, while ensuring that all the core math remains feasible for recovery, requiring nothing beyond paper, a calculator, and specific instructions.
DuraShare combines three existing, well-established cryptographic techniques: (1) Shamir Secret Sharing over GF(2053), the smallest prime field containing the 2048-word BIP39 list; (2) 2D error detection, applying row and column checksums to each share to protect the data against transcription errors and physical damage; and (3) an optional affine inner-product MAC over the same finite field that, when the corresponding key material is separately held and uncompromised, provides bounded detection of active share substitution before secret reconstruction.
To demonstrate recovery independence, the workshop includes two live demos: the whole process using a single-file HTML tool (designed for air-gapped environments like Tails OS), followed by a hands-on, step-by-step paper-and-calculator recovery of a single row (3 words and a checksum) using printed templates.