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 3.5.5 27 Jan 2026

library(jose)

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "JiW8QRHABDqYL9ZAl0Zun37Fu3hmKAnwxF0rDh_DrQk",
    "y": "SbPdcTcjN0t_90ImOm58l_h7SwDJ2ooWKKXiVVr9R8Q",
    "d": "qWmbm2AMSje02qECCl69zMw41se6LjR7NNQwefDLwqM"
}
 

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "JiW8QRHABDqYL9ZAl0Zun37Fu3hmKAnwxF0rDh_DrQk",
    "y": "SbPdcTcjN0t_90ImOm58l_h7SwDJ2ooWKKXiVVr9R8Q"
}
 

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

[256-bit ecdsa public key]
md5: aaf35548875e2133688fe0cbba593786
sha256: 48e9752aab6d171d5d838ee3ea000579097cc6e0eb45851d98e6bbd0900a719a

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] 72 7b 51 9e 94 06 c2 71 3c 86 20 ce 57 33 e1 6c

(jwk <- write_jwk(key))

{"kty":"oct","k":"cntRnpQGwnE8hiDOVzPhbA"} 

read_jwk(jwk)

 [1] 72 7b 51 9e 94 06 c2 71 3c 86 20 ce 57 33 e1 6c