Yuzu (Nintendo Switch emulator)

yuzu's logo from 2019 to present.

Yuzu, stylised as yuzu, is a Nintendo Switch emulator. Its claim to fame includes being lead by the same staff and developers that manufactured the flagship Nintendo 3DS emulator, Citra. During the 3DS's lifecycle, Citra was held to high regards by the 3DS emulation community.

Launching in 2018, only a year after the Nintendo Switch's release in March 2017, yuzu has been met with controversy, primarily stemming from its availability for a highly recent console, as well as being financially supported via a paid donation system for early-access builds and prioritised support.

Fast forward to 2024, and you'll see yuzu as tremendously capable emulation software, running a large amount of Switch software as well as or better than a real Nintendo Switch console. yuzu is available for PC, Mac, Linux, and Android.

Preliminary

As seen in Why The Switch Still Excites, Nintendo's role as a console manufacturer includes a responsibility to create an ecosystem for developers to create and publish video games. Part of this responsibility includes ensuring that third-party developers can trust Nintendo's platforms, like the Nintendo Switch, to uphold the developer's copyright, by ensuring that theft of their intellectual property does not occur.

From the Nintendo Entertainment System in 1985, Nintendo can be seen as the sole saviour of the video game market, previously rife with bootlegged software distribution and lackluster financial security. By moderating the ecosystem and enabling a common ground for consumers to play their games, eliminating the necessity for proprietary hardware for individual games, and implementing technological protection measures to prevent intellectual property theft, developers flocked to Nintendo as a video game platform and publisher. Nintendo solely decides which games are playable on their console via a series of hardware and software protections, protecting developers from the copying and distribution of bootlegged software - unlike any console that came before it. Nintendo originated as a playing card company from the 1800s, but video games are their legacy, especially ensuring their success as a company in the later years of its formation. Nintendo's success is a direct result of combating software pirates, and it should come as no surprise that Nintendo wants to protect itself from the consequences that led to the market original demise.

Games released and published by Nintendo currently are protected with numerous copyright protection measures to this day. The Nintendo Switch's operating, Horizon, is an example of flagship security-grade software, and Nintendo's most expansive and technically complicated OS. For example, to date, Horizon publicly has zero exploitable software vulnerabilities that enable high-severity attacks, such as kernel or TrustZone takeover, both of which can lead to the possibility of software piracy. Nintendo invests heavily in the security of its platform, and is widely known to use its position in the industry to deter and set examples for those who threaten it.

However, in early 2018, a bootROM exploit for NVIDIA's Tegra X1 APU, known as CVE-2018-6242 (fusee-gelee), was documented and disclosed to NVIDIA, before later being disclosed to the public. As this particular APU is not only used in the Nintendo Switch, but devices such as the Google Pixel C tablet and Nvidia Drive autonomous driving framework, it was necessary to inform NVIDIA of the exploit before the general public to prevent malpractice from bad actors, which could have dire implications. Because a bootROM runs before any piece of Nintendo's code, exploits within it bypass a vast majority of Nintendo's hardware security measures that protect the Nintendo Switch and its software. Fusee-gelee was a monumental discovery for reverse-engineering and documenting the Nintendo Switch.

This allowed further and widespread documentation of the Nintendo Switch, especially useful for emulator development. As it bypasses nearly all of Nintendo's security measures, its existence allows exploiters to obtain copies of their Nintendo Switch console's encryption keys, which are unique to every console, before access to those keys are revoked by the operating system. These keys are used in conjunction with others to descramble (decrypt) internal system data, as well as Nintendo's game data.

End-users can take advantage of this bootROM exploit to dump (copy) data from their Nintendo Switch, which (when used in conjunction with an emulator, like yuzu) allows the user to run copies of Nintendo Switch software without using a Nintendo Switch.

Litigation

On its own, using Nintendo Switch games without using the Nintendo Switch may appear to resemble a conflict of interest within Nintendo. In February 2024, Nintendo filed a suit against the company that develops yuzu, Tropic Haze. The suit details and cites violations of Nintendo's copy-rights, as well as seeks damages from the theoretical harm caused by the existence of yuzu.

A full overview of the litigation documents can be found here. Feel free to read along with my comments after opening this link in a new tab.

The rest of this page will have my opinions on each document. I am not a lawyer, and I do not have information internal to either Nintendo or the yuzu team.

Page 1

Tropic Haze is the name of the LLC that develops yuzu. It is new to me that yuzu's development team is under a company, whereas I was under the impression that it was an unstructured organisation with freelance participants on GitHub, Discord, and Patreon.

It's awfully annoying how Nintendo assets what is lawful and unlawful; in litigation, whether or not something is illegal or not is not up for the plaintiffs to assert without immediately citing where their rights were violated. Instead, it's more accurate for the plaintiff's to claim that their rights were violated by the defendant, and proceeding to show examples of where.

Page 2

For me, it's a bit curious to see Nintendo refer to the encryption key dump with the community name "prod.keys". Does this collection of keys have an official name in-house? Does Nintendo organise console-unique keys on a more granular scale instead?

Page 3

Nintendo doesn't cite where Bunnei, yuzu's lead developer, asserts that "most" users pirate encryption keys. Their later citation for Bunnei's quote makes no mention of the quantity or severity of this issue. In addition, it is odd that Nintendo is choosing to hold yuzu directly responsible irresponsibility on the user's end, despite efforts being put in place to prevent and deter piracy on yuzu's end. To this day, even after litigation, yuzu upholds an anti-piracy stance and enforces it strictly and swiftly. Even a web browser, especially with extensions, can be used primarily to pirate property. Yet, Microsoft or Google are not held responsible for the actions of their users by owners of intellectual property.

Page 4

Nintendo's lawyers are seemingly focussing on the encryption keys more than the emulator itself. A few months ago, LockpickRCM, software monumental to decrypting data from a Nintendo Switch, was recently eliminated from GitHub following a DMCA takedown request from Nintendo. This has no relation to yuzu itself. yuzu is merely taking data entirely provided by the user, and processing the output. If Nintendo considers the keys to be an illegal number, yuzu has no hand in providing users with said keys.

More importantly, Nintendo cites section 1201 of the Digital Millennium Copyright Act, an act that protects copyright holders from tampering and unauthorised access to copyrighted works as a result of tampering with copyright protection measures. DMCA is not necessarily limited to audiovisual works, instead acting as a barrier to reverse engineering as a whole for any embedded device protected by copyright, such as the Nintendo Switch itself. The legality of reverse engineering has implications on sectors wildly outside the scope of a video game emulator, and is often associated with Right to Repair as well; RE work customarily needs to be done to ensure compatibility with repair parts that aren't distributed or manufactured by the OEM. Any kind of ruling or precedent based on Nintendo's claims here will be monumental for many sectors of my personal life, including repairs and homebrew.

Nintendo notes how yuzu is meant to operate primarily on Switch consoles. They continue to raise a point about software licensing, which is valid, but untested in court. Software, such as Nintendo Switch video games, are licensed; not sold, to users. This means that video games remain Nintendo's intellectual and physical property, even after you pay them for the license to play it. When games are distributed but not protected by any sort of technological protection measure, it is legal to make backups of software. However, license agreements, such as Nintendo's license agreement that disallows users from making backup copies, are now to be tested in court. License agreements are more often upheld in favor of the licensor, but not always.