A rough list of Qualified Electronic Signature certificate issuers which operate specifically in Lithuania.
All of the listed issuers provide two certificates as a bundle:
Platforms: smartcard
Previously known as: Nacionalinis sertifikavimo centras (NSC), Asmens dokumentų išrašymo centras (ADIC)
MD (aka ADIC) is the issuer for Lithuanian national identity cards (LT eID), which serve primarily as a physical document (ICAO-compliant MRTD) and only secondarily as qualified signing devices.
The physical eID cards have gone through various vendors, from Gemalto in 2008 to the Polish PWPW to CryptoTech, and most recently MaskTech.
The newest MaskTech cards have a unified interface – both the "smartcard" and "ICAO MRTD" applets are accessible through NFC and electrical interfaces alike (whereas previously the ICAO MRTD NFC chip was entirely separate from the smartcard proper). MaskTech provide an "mCard LTU" Android app which
Platforms: smartcard, SIM, Android/iOS ("LT-ID")
RCSC is a "state enterprise" (government-owned company) responsible for managing various registries and IT systems, with a history of being a bit full of themselves.
RCSC have been issuing certificates on traditional USB smartcards (mostly SafeNet/Thales) for many years. For a short while, they also worked with mobile operators as the issuer for on-SIM "mobile ID" certificates (which all have since moved to EID-SK).
Recently, "LT-ID" is their attempt to compete with Smart-ID in the "smartphone app" territory, but is still very rough. (The Android app feels like an early access alpha – with hardly any updates or maintenance since its initial release – and the official LT-ID website doesn't even bother providing a direct sign-up link; one needs to google for "Registrų Centro savitarna" and figure out which of the several self-service sections is related to LT-ID.)
Platforms: SIM ("Mobile-ID"), Android/iOS ("Smart-ID")
EID-SK is an Estonian company doing business in all three Baltic states.
They are currently the issuer for SIM card "Mobile-ID" certificates for all three mobile operators.
They also provide the "Smart-ID" app for Android/iOS, which uses a scheme of splitting an RSA key into separate shares between the user's device and the company's remote HSM, to prevent key leakage (many smartphones at the time did not yet have a secure element) while still having the user at least technically in possession of the Signing Device.
Both Mobile-ID and Smart-ID have wide adoption in various services, largely for user authentication.
Platforms: Android/iOS
A Lithuanian/Swedish company. Little known about them.
They issue certificates solely through the "ZealID" smartphone app. Similar to Smart-ID, both an authentication certificate and a qualified signature certificate are issued. However, ZealID seem to focus on document signing exclusively through their own platform (a web app similar to that of Dokobit), and there is zero adoption of the app for authentication or signing in any third-party services.
Platforms: smartcard (USB eToken)
SSC was a small company providing CA services (apparently for a long time; they seem to have participated in the EuroPKI project in 1999).
They used to sell qualified signing certificates on physical Aladdin eToken 72k, alongside providing web (TLS) and S/MIME certificates.