Create RSA Key Pairs in Your Browser Generate RSA key pairs using the Web Crypto API.

The tool works by utilizing the Web Crypto API's SubtleCrypto interface to generate a pair of public and private keys using the RSA-OAEP algorithm with a modulus length defined by the user's selected key size. This process involves generating large prime numbers p and q, then calculating n as their product and selecting e as 65537, a commonly used value for its relatively small size and ease of calculation. The corresponding private exponent d is calculated such that e*d = 1 mod phi(n), where phi(n) represents Euler's totient function applied to n.

When the user initiates key generation, it triggers an asynchronous call to window.crypto.subtle.generateKey with parameters specifying RSA-OAEP as the algorithm and defining the public exponent. The generated keys are then exported in SPKI (Subject Public Key Information) format for the public key and PKCS#8 format for the private key using the SubtleCrypto interface's exportKey method, resulting in ArrayBuffer objects that contain the encoded key data.

These ArrayBuffers are subsequently converted to base64 strings through a process involving creation of Uint8Array views from the buffers, followed by transformation into binary strings and finally application of btoa function for base64 encoding. The formatted PEM (Privacy Enhanced Mail) strings are then constructed by wrapping these base64-encoded strings with headers indicating whether they represent public or private keys.

Key sizes such as 1024 bits, 2048 bits, and 4096 bits determine the modulus length in the RSA-OAEP algorithm used for key generation. A minimum recommended key size of 2048 bits is typically suggested to ensure sufficient security against factorization attacks on n. The generated public and private keys are then presented to the user within textareas, where they can be easily copied using provided copy buttons that invoke a function utilizing the copyToClipboard utility from the utils library.

The tool's use of React state management with useState allows it to maintain an up-to-date representation of key generation status and any generated keys. Once keys are successfully generated or if an error occurs during this process, updates to relevant states trigger re-renders that display the resulting public and private keys in PEM format to the user.

Implementation details like handling different button click events for key size selection and copy functionality rely on React's event handling mechanisms, alongside its useCallback hook to memoize functions such as generateKeys and handleCopy. By using these technologies and APIs, it efficiently generates RSA key pairs within a web-based environment while ensuring private keys remain secure by never leaving the user's browser.