# LS on LI Requirements on IMS Data Channel

## Document Information
- **Meeting:** SA3-LI#97 (29 April – 02 May 2025, Washington DC)
- **Document Number:** S3i250185
- **Release:** Rel-19
- **Work Item:** LI19
- **Source:** SA3-LI
- **To:** SA4, SA2
- **Cc:** CT1, SA3

## Overall Description

### Problem Statement

SA3-LI has identified critical gaps in the current IMS Data Channel encryption architecture that prevent CSPs from meeting lawful interception (LI) requirements specified in TS 33.126, particularly requirements R6.4-160, R6.4-170, R6.4-180, and R6.4-190, including mid-session interception scenarios.

### Key Issues Identified

#### 1. Encryption Architecture Limitations

The current encryption and architecture design for IMS Data Channel fails to meet LI requirements in the following scenarios:

- **Roaming cases** with S8HR/N9HR model
- **Interoperability cases** between two CSPs
- **Direct communications** between two users (when at least one is an LI target)

#### 2. LI Access Requirements Not Met

SA3-LI specifies two acceptable approaches for LI:

1. **Preferred:** Access to a copy of communication content without confidentiality protection
2. **Required (if preferred not feasible):** Access to encryption parameters that enable decryption of encrypted content

Neither approach is currently achievable with the existing IMS Data Channel implementation.

#### 3. Interoperability Gap

When two CSPs interoperate where:
- One CSP uses IMS Data Channel
- The other CSP uses IMS without IMS Data Channel feature
- The LI target is on the CSP without Data Channel

The CSP cannot intercept and provide the content exchanged between the two users, creating a compliance gap.

### Reference Architecture

The document references Figure 6.2.10.1-1 from TS 26.114 showing the Data Channel Workflow, indicating the architectural context of the identified issues.

## Impact

These limitations create **major complications for CSPs to respect their national regulations** regarding lawful interception obligations.

## Action Requested

SA3-LI requests SA4 and SA2 to:

**Develop a solution and architecture for secured IMS Data Channel that enables CSPs to meet the LI requirements as described in TS 33.126.**

## Next SA3-LI Meetings

- **SA3LI Meeting #98:** 15th – 18th July 2025, Florence, Italy
- **SA3LI Meeting #99:** 4th – 7th November 2025, TBD, USA