Description
The Digital Signature Algorithm (DSA) is a standardized public-key cryptography algorithm for creating and validating digital signatures. It is defined in the U.S. Government's Federal Information Processing Standard (FIPS) 186. Within the 3GPP ecosystem, DSA is referenced and utilized in various security specifications to provide data integrity, authentication, and non-repudiation services. The algorithm operates on the mathematical principles of the discrete logarithm problem in a prime-order subgroup of a finite field. A digital signature proves that a message was created by a known sender (authentication), that the sender cannot deny having sent the message (non-repudiation), and that the message was not altered in transit (integrity).
The technical workings of DSA involve a key pair: a private key known only to the signer and a public key that is widely distributed. The signing process uses the private key and the message hash to produce two integers, r and s, which constitute the signature. The verification process uses the signer's public key, the original message, and the received signature (r, s) to compute a value that must match the r component of the signature if the signature is valid. DSA's security relies on the computational difficulty of solving the discrete logarithm problem. In 3GPP specifications, the use of DSA is often specified alongside other algorithms like RSA or ECDSA, with specific key lengths and parameter sets (e.g., L=2048, N=256 as per FIPS 186-4) mandated for different security strengths.
In the 3GPP architecture, DSA can be applied in several contexts. It is specified for use in the Authentication and Key Management for Applications (AKMA) framework to allow applications to leverage 3GPP credentials. It is also used in the security specifications for network management interfaces (e.g., the Itf-N interface) to protect management data. Furthermore, DSA may be employed in the context of Lawful Interception (LI) and the Security Assurance Specification (SCAS) for securing network functions. Its role is to provide a verifiable and standardized method for ensuring the trustworthiness of critical signaling, management commands, or application-level authentication tokens within the 5G core and beyond.
Purpose & Motivation
DSA was developed and standardized by NIST to provide a secure, efficient, and government-approved algorithm for digital signatures, offering an alternative to the RSA algorithm. Its purpose within 3GPP specifications is to furnish a cryptographically strong, standardized mechanism for achieving authentication, integrity, and non-repudiation in various parts of the telecommunication system. This addresses the fundamental security problem of verifying the origin and integrity of data in a potentially untrusted network environment, especially as services become more software-based and exposed to broader threats.
The motivation for including DSA in 3GPP standards stems from the need for algorithm agility and compliance with various national and international security regulations. While 3GPP systems have historically used symmetric cryptography (e.g., MILENAGE for authentication) and other asymmetric algorithms, DSA provides a specific, well-vetted option for use cases requiring formal digital signatures. It addresses limitations of purely symmetric systems, which cannot provide non-repudiation, and offers a standardized alternative to RSA, which is based on a different mathematical problem (integer factorization). Its inclusion, particularly from Release 8 onwards, reflects the expanding scope of 3GPP systems to support more generic application security (like AKMA) and secure management planes, where standardized public-key signature algorithms are a necessity.
Key Features
- Public-key cryptography based on the discrete logarithm problem
- Generates a signature pair (r, s) from a message hash and private key
- Provides data integrity, authentication, and non-repudiation services
- Standardized in NIST FIPS 186 with defined parameter sets (e.g., 2048-bit keys)
- Used in 3GPP for AKMA authentication and management interface security
- Offers an alternative standardized signature algorithm to RSA and ECDSA
Evolution Across Releases
Introduced references to the Digital Signature Algorithm within 3GPP security specifications, notably for securing management interfaces. Established its use as a standardized cryptographic primitive for digital signatures to provide integrity and non-repudiation for network management data and potentially other signaling.
Enhanced the specification of cryptographic algorithms, potentially including updates to the recommended key lengths or usage guidelines for DSA in line with evolving cryptographic best practices and standards like updated NIST guidelines, ensuring continued security strength.
Expanded the application of DSA within the new 5G security architecture. Specified its use in the Authentication and Key Management for Applications (AKMA) framework, allowing application functions to securely authenticate using 3GPP credentials via digital signatures.
Further integrated DSA into enhanced security mechanisms, including those for service-based interfaces and network exposure. Continued alignment with international cryptographic standards to maintain robust security for 5G core network functions and management systems.
Defining Specifications
| Specification | Title |
|---|---|
| TS 32.808 | 3GPP TR 32.808 |
| TS 33.303 | 3GPP TR 33.303 |
| TS 33.885 | 3GPP TR 33.885 |
| TS 33.969 | 3GPP TR 33.969 |