RSA modulus size is the length of an RSA key, measured in bits. It determines the scale of the mathematical numbers used by RSA and strongly affects security and performance. section 6.3.1 section 7.3
Larger RSA keys generally provide stronger security, but arithmetic on them requires more computation, consumes more battery on mobile devices, and can increase operating costs. Choose the minimum length required by current corporate security standards. section 6.3.1 section 7.3
Use these practical reference points when selecting an RSA modulus size:
- Treat RSA 2048-bit keys as secure today, while preferring 3,072- or 4,096-bit keys when stronger margins are required. section 6.3.1
- Recognize 4,096-bit RSA keys as substantially larger and slower than shorter keys, especially on constrained devices. section 7.3
- Compare RSA with ECC before starting a new application: a 256-bit ECC key is described as offering security comparable to RSA-3072 with better performance. section 7.3
Choosing between RSA key sizes
A service using RSA 2048-bit keys meets the stated current security level. A team requiring a larger security margin can select RSA 3072 or RSA 4096, accepting higher computational cost and checking corporate guidance first. section 6.3.1 section 7.3
