# An SSI-Based Solution to Support Lawful Interception
## 3 Motivations and Goals  
The literature includes several proposals for standardizing the interceptions between the NO and the LEA, as well as between the NO and the LEMF, such as CALEA [7], 3 GPP TS 33.108 [8], ITU-T Y2770 [9], and ETSI TS 101 671 V3.15.1 [10]. Among them, the latter is the most recent and used one in LI. However, to the best of our knowledge, the interaction between the LEMF and the LEA is not explicitly addressed in ETSI TS 101 671 or other standards, and the lack of a structured framework for LEA-LEFM interactions introduces three main issues:  
1. Interoperability issues: The absence of interoperability standards led each country to adopt and implement its own national procedure to manage the interaction regarding how LEA should retrieve data from LEMF [12]. These methods are often incompatible with each other. This limitation becomes particularly critical in cross-border investigations, where an LEA may need to delegate interception access to an external agency. For example, consider a scenario where an EU member state is investigating a transnational criminal group. The national LEA may require assistance in accessing intercepted communications related to the group's activities. In this case, the LEA can request support from an external agency, such as the NSA, which is the U.S. government agency responsible for foreign and domestic intelligence and counterintelligence purposes. This agency can facilitate access to the necessary data from LEMFs in other states. In this case, proper authorizations should be granted by the LEA to the external agency ensuring that the data are handled in accordance with legal requirements. 2. Procedural inefficiencies: Many lawful interception processes continue to rely on manual and insecure procedures, such as paper-based approvals and email exchanges. These mechanisms could result in operational inefficiencies and human errors and may introduce delays in investigations in which rapid access to the intercepted information is crucial. 3. Security risks: Security risks may arise due to the absence of standardized access control mechanisms. Without a protocol for managing and verifying access to intercepted data, there is no robust way to ensure that only authorized entities retrieve sensitive information. This exposes LI systems to several vulnerabilities, including unauthorized data retention, insider threats, and data leaks. Additionally, the lack of real-time access revocation mechanisms means that once an external agency is granted access to LI data, it may retain that access indefinitely, even after the investigation has concluded, increasing the risk of unauthorized disclosures and violations. To address these challenges, we propose a decentralized and verifiable credential system based on the SSI paradigm. Our solution ensures that only authenticated and authorized entities can retrieve intercepted data while enabling real-time revocation of access rights to prevent misuse. Our solution provides the following outcomes:  
* Fine-tuning: The agency obtains a credential for access to data specific to a certain request, including a validity period to verify whether the authorization has expired;
* Minimality: Data accessed by the agency is selectively disclosed, supporting the principle of minimal information disclosure;* Revocation: Authorizations can be revoked by the issuer at any time, a significant advantage over standard signature-based solutions where only certificates can be revoked, not specific signatures;
* Automation: Authorizations are machine-readable, enabling fully automated authorization processes;
* Effectiveness: We provide a proof of concept based on established SSI standards, such as the Sovrin framework. To better understand the points above, we anticipate some details of the solution. The LEA can play the role of the issuer and release some credentials (i.e., authorizations) to the agency. On the other hand, the LEMF can play the role of the verifier and check the credentials presented by the agency.