ecdh-aes-gcm-example.js

(async () => {
  const keyPair = await crypto.subtle.generateKey(
    {
      name:'ECDH',
      namedCurve:'P-256'
    },
    true,
    ['deriveKey', 'deriveBits']
  )
  
  const nonce = await crypto.subtle.deriveBits(
    {
      name: 'ECDH',
      public: keyPair.publicKey
    },
    keyPair.privateKey,
    16 << 3 // 16 bytes
  )

  const key = await crypto.subtle.deriveKey(
    {
      name: 'ECDH',
      public: keyPair.publicKey
    },
    keyPair.privateKey,
    {
      name: 'AES-GCM',
      length: 256
    },
    true,
    ['encrypt', 'decrypt']
  )
  
  const encryptedMessage = await crypto.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv: nonce
    },
    key,
    new TextEncoder().encode('ciao mondo')
  )
  
  const decryptedMessage = await crypto.subtle.decrypt(
    {
      name: 'AES-GCM',
      iv: nonce
    },
    key,
    encryptedMessage
  )
  
  console.log(new TextDecoder().decode(decryptedMessage))
})()