SIM-Based A2P SMS Encryption for Secure OTP Delivery
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Solution Overview
Problem
Existing A2P SMS delivery is vulnerable to interception, allowing fraudsters to decipher one-time-passwords or transaction numbers, which is a significant concern for mobile banking and ecommerce, especially on feature phones lacking smartphones or internet access.
Innovation Solution
A method for secure A2P SMS communication using pre-shared keys and encryption algorithms, delivered via SMS Over-the-Air (OTA) mechanism to Subscriber Identity Modules (SIMs), enabling encryption and decryption without requiring smartphones or internet access, leveraging existing SMS specifications and infrastructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SMS encryption is implemented using SIM Toolkit and end-to-end encryption, then security against interception is improved, but system complexity and deployment difficulty increase due to requirements for coordination between banks, mobile operators, and SIM card vendors
Solution Approach 1:
The patent introduces an SMS Firewall as an intermediary component deployed at the mobile operator's network node. This firewall acts as a mediator between the A2P sender and the subscriber, performing encryption and decryption operations without requiring complex coordination between multiple parties. The firewall handles the security functions that would otherwise require SIM Toolkit coordination, thereby reducing system complexity while maintaining security.
Solution Approach 2:
The patent enables the subscriber's SIM card to perform self-service encryption and decryption using pre-shared keys stored in the SIM. The SIM automatically handles the security operations for incoming A2P SMS messages without requiring external intervention or complex configuration. This self-service approach eliminates the need for coordinated deployment across multiple organizations while maintaining end-to-end security.
2Reliability
If SIM Toolkit-based encryption is used, then security is improved, but scalability is reduced because the solution is specific to particular banks and difficult to scale across multiple banks and mobile operators
Solution Approach 1:
The patent creates a universal solution that works across multiple banks, mobile operators, and device types by standardizing the encryption approach. The SMS Firewall implements a common encryption framework that can serve different A2P senders (banks, operators) and different subscriber types (smartphones, feature phones) without requiring bank-specific or operator-specific customization. This multi-functional approach enables scalability across the entire mobile subscriber base.
Solution Approach 2:
The patent uses parameter changes to adapt the encryption solution to different scenarios. By changing the encryption parameters (using pre-shared keys instead of SIM Toolkit, supporting both smartphone and feature phone environments), the system can maintain security across different platforms and operators without requiring fundamental changes to the overall architecture. This flexibility enables widespread deployment across multiple banks and operators.
3Reliability
If modern smartphone-based mobile banking with dedicated applications is used, then functionality and security are improved, but accessibility is reduced because it requires smartphones and internet access, excluding feature phone users
Solution Approach 1:
The patent uses disposable pre-shared keys that are independently generated for each A2P SMS message. These keys are not stored long-term in the SIM but are provided temporarily for the specific encryption operation. This approach provides strong security without requiring permanent cryptographic infrastructure in the SIM, making it suitable for both smartphones and feature phones without requiring internet access or dedicated applications.
Solution Approach 2:
The patent segments the security function between the network side (SMS Firewall) and the subscriber side (SIM card). The firewall handles the complex encryption operations for A2P messages, while the SIM only needs to store and process the pre-shared keys. This segmentation allows feature phones with limited processing capability to participate in secure messaging without requiring the full smartphone-based banking ecosystem.
Data Source
AI summary
The present invention relates to a method for secure Application-to-Person, A2P, short messaging service, SMS, communication at a network node. The method comprises receiving an A2P SMS from an A2P sender for delivery to a subscriber and determining that the A2P SMS requires secure A2P SMS delivery to the subscriber. The method also comprises encrypting a payload of the A2P SMS using at least one pre-shared key, PSK, and an encryption algorithm, wherein the at least one PSK and the encryption algorithm have been securely provided to a SIM associated with the subscriber. The method further comprises encoding the encrypted A2P SMS payload to obtain an encoded A2P SMS payload and relaying the encoded A2P SMS payload to the SIM. A method for communication at a subscriber device comprising a SIM associated with a subscriber.