Reading/Writing JSON Web Keys (JWK) in R

RSA / ECDSA keys

JSON Web Keys (JWK) is a format specified in RFC7517 for storing RSA/EC/AES keys in a JSON based format. It can be used to import/export such keys in the browser using the new W3C WebCryptoAPI.

The jose package makes it easy to read/write such keys in R for use with JWT or any other functionality from the openssl package.

library(openssl)

Linking to: OpenSSL 3.0.13 30 Jan 2024

library(jose)

# Generate a ECDSA key
key <- openssl::ec_keygen()
jsonlite::prettify(write_jwk(key))

{
    "kty": "EC",
    "crv": "P-256",
    "x": "zdo16OQZZA330ezUIZCvvNrmvFn1AgkkVYVeFqJz9JQ",
    "y": "gRSeV_mmrj2ZrxMSGZV1LnWxBFJesLaYqBnTgaOJj-c",
    "d": "sDzk3Ok2WI76VOkkcWJ-GKi3jCuOq8GL4KXpsNMYBhA"
}
 

# Use public key
pubkey <- as.list(key)$pubkey
json <- write_jwk(pubkey)
jsonlite::prettify(json)

{
    "kty": "EC",
    "crv": "P-256",
    "x": "zdo16OQZZA330ezUIZCvvNrmvFn1AgkkVYVeFqJz9JQ",
    "y": "gRSeV_mmrj2ZrxMSGZV1LnWxBFJesLaYqBnTgaOJj-c"
}
 

# Read JWK key
(out <- read_jwk(json))

[256-bit ecdsa public key]
md5: 92a5675ada11c18b78734f8fa29e6ccf
sha256: 2352e97b4d836e8a1d6794041fd4a68d5f757aa5a61e9bad8c8f95ccbdf4b6ed

identical(pubkey, out)

[1] TRUE

AES/HMAC keys

JWT also specifies a format for encoding AES/HMAC secrets. Such secret keys are simply raw bytes.

# Random secret
(key <- rand_bytes(16))

 [1] 50 8a f7 5c 2b d4 14 52 43 5c 91 5a 38 0e 19 64

(jwk <- write_jwk(key))

{"kty":"oct","k":"UIr3XCvUFFJDXJFaOA4ZZA"} 

read_jwk(jwk)

 [1] 50 8a f7 5c 2b d4 14 52 43 5c 91 5a 38 0e 19 64