# How RSA Public-Key Encryption Secures Digital Messages

> This patent describes the RSA public-key cryptographic system, a method for securely sending digital messages by using a public key to encrypt and a private key to decrypt, based on the mathematical difficulty of factoring large numbers.

- **Patent:** US 4405829
- **Original title:** Cryptographic communications system and method
- **Owner:** Massachusetts Institute of Technology
- **Granted:** 1983
- **Status:** Public domain (expired)
- **Times cited:** 1,015
- **Field:** telecommunications, software, ecommerce, fintech, cybersecurity, consumer_electronics

**Full plain-English explainer:** https://patentbrief.org/patent/us/4405829/rsa-encryption

**Original patent:** https://patents.google.com/patent/US4405829

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._