Node - Get Public Key From Private Key with JavaScript

I had to do this for a project that uses AWS EC2 key pairs because AWS only provides you with the private key when you create a key pair, at least as far as I could figure out.

Here's a sample of the code I used to convert private keys into public keys with JavaScript on NodeJS, it uses the "node-forge" cryptography library that is available on npm.

// Forge crypto package for node (https://www.npmjs.com/package/node-forge) var forge = require('node-forge'); // PEM-formatted private key var privateKey = `-----BEGIN RSA PRIVATE KEY----- MIICXAIBAAKBgQCOEDvAy4g+MCLUDGk2ybxmXPR3ETXwlfAZo5lS5bDWDZe/uvMF 83VtN+Sf/AcRJ3A3F46vgKSaoe/38hXM4w/ADbUY5wWXAyeMf6y4kujOy/IxX2Ls YYFkp6D085S1Ot69gKwodYnnwHxAZaREGC+jMTOwPRzK+Iz7aOrlBqPP9QIDAQAB AoGANy43B3wHP6CS5qqrc4yIkXoputYEjZ6v1EWnmHt/ZKWC/AYxv24BfprnQv0y AYfAHqYX1jOxvB6Kh1SRAzRvOSCnGmowLjZnG4aIfkN4pj5WKNk9BdGqy1oNfH3M 3JbuG5cxRowMiY3nOzIsbys9c2M3lEGNlqwz/FfPPUsyLUECQQD4+6lkcwKKJnLN HG4ZM0chsyBJeFMmy+Z8mWHE5wrgP0+OqwCI8fg0neYMfQ1bkWxNzJtHm3kIZkKh sQjVw3THAkEAkhEtr9dc5OsJeEaMU4FMiufx4EalT3WkvI9QId9xCJ1P9rPIiM0j kxn1C1v6KMe94YW9VbU1rmURKEvUhgAhYwJBAMJjwYHiZUY09IZ9Ptw/87Y04u1Z mxn8Mcxv+CxB8nTYGSYbDkTdHdr+uGBhte8a38LyDv3ePaW4KSeST4KNonsCQBZ9 ApWyCKFN9nVIF06793bjYv/uoIDtUeGeBu5QImz7G1aWM2esfa+mLW4ESS2CIx/X oWDSt2MUOGIF2sCOwJUCQFSsxf5dzUjHRy4G3xaM0uqg70PUfPwYm7/jSoO734tZ D8TrVoeYNZDvjZyVa7/jghMeKHAwRKyT8L2dmukEyJY= -----END RSA PRIVATE KEY-----`; // convert PEM-formatted private key to a Forge private key var forgePrivateKey = forge.pki.privateKeyFromPem(privateKey); // get a Forge public key from the Forge private key var forgePublicKey = forge.pki.setRsaPublicKey(forgePrivateKey.n, forgePrivateKey.e); // convert the Forge public key to a PEM-formatted public key var publicKey = forge.pki.publicKeyToPem(forgePublicKey); // convert the Forge public key to an OpenSSH-formatted public key for authorized_keys var sshPublicKey = forge.ssh.publicKeyToOpenSSH(forgePublicKey); console.log(` PEM-formatted public key: ${publicKey} OpenSSH-formatted public key: ${sshPublicKey} `);