I want to use the asymmetric encription offered by a tool to encrypt my files and I would like to know if the following encryption process works, regardless of perhaps not optimal use.

  • Generate a 32-bytes-random-key inside the browser with window.crypto.getRandomValues

  • use sjcl crypto library for:

    • choosing AES algorythm cipher.aes
    • generating 4 words random IV vector random.randomWords(4, 0)
    • encrypting a file in GCM mode mode.gcm.encrypt (tag 128 bits)
    • concating IV and encrypted output producing the binaryFile1
  • use NaCl Networking and Cryptography library, through a tool that implements ECIES, for:

    • generating an encryptionKeypair using nacl.box.keyPair.fromSecretKey
    • encrypting the above 32-bytes-random-key with the ephemeralPublicKey (using the x25519 part of the schema x25519-xsalsa20-poly1305) producing the binaryFile2, a bundle containing the encrypted AES key and, among other metadata, the ephemeralPublicKey.
  • concat binaryFile2 + a-separator + binaryFile1 producing finalBinaryFile

  • keep the finalBinaryFile on the cloud until it is necessary to download it and then decrypt it through the reverse process using the secretKey I own.

To encrypt the files I could directly use the symmetric key keeping it safe but I would like to use a DB of shared static public keys, whose trustness I can assume valid.

  • $\begingroup$ What is the question? $\endgroup$
    – kelalaka
    May 11, 2022 at 10:41
  • $\begingroup$ I made the question explicit in the title. Thank you. $\endgroup$
    – blockmined
    May 11, 2022 at 10:44
  • 2
    $\begingroup$ Why don't you use well-maintained programs like Veracrypt or libraries like the age (age is a simple, modern and secure file encryption tool, format, and Go library.) $\endgroup$
    – kelalaka
    May 11, 2022 at 10:46
  • 1
    $\begingroup$ Complete reviews of cyptographic protocols and schemes is off topic. Using ECIES to encrypt a secret key is a bit spurious; you could use the key agreement part itself to establish a key. Of course, you'd also need to send the ephemeral public key for ECIES, something that is missing in your protocol. I don't see how you've established the static key pair of the receiver or how that public key is trusted, so the description is certainly not without fault nor complete. $\endgroup$
    – Maarten Bodewes
    May 11, 2022 at 12:27
  • $\begingroup$ Thank you for your remarks Maarten. Actually I forgot to mention that in the binaryFile2 there is also the ephemeral publick key so I will update the question. I am aware that I am asking about the validity regardless to the process of registration of the static key pair and relative trustness. $\endgroup$
    – blockmined
    May 11, 2022 at 12:47

1 Answer 1


NaCL provides a set of crypto_box methods which do this all in one go. Libsodium provides an even easier set of crypto_box_easy methods.

  • $\begingroup$ Thank you for your suggestion, My implementation has to be in javascript so I am just using a wrap of NaCl set that offers and manages key pair generations. $\endgroup$
    – blockmined
    May 11, 2022 at 14:39
  • 1
    $\begingroup$ There are JS bindings for libsodium as well. $\endgroup$ May 11, 2022 at 17:57

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