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": "0k4G_wwYnYCGOgm_5nRVh02w2VNijr9cRmPmxUy110k",
    "y": "nqbGHoE-tZ1l7D6ePvdW4pan8DfBRWcop9Fo0geKvfQ",
    "d": "eRh0mvRYyv5AL_dnH-JjTAEqaMlPAPoqVCOd-J2tZss"
}
 

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "0k4G_wwYnYCGOgm_5nRVh02w2VNijr9cRmPmxUy110k",
    "y": "nqbGHoE-tZ1l7D6ePvdW4pan8DfBRWcop9Fo0geKvfQ"
}
 

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

[256-bit ecdsa public key]
md5: d0e44db83b391ff11f6576b660c2fa49
sha256: 9643e292ce9129bb255af3e3b4263365b645d17c0760247def919c86cc72cd92

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] 0b 92 02 03 15 00 22 9b 2b 38 e1 d7 69 50 2d e0

(jwk <- write_jwk(key))

{"kty":"oct","k":"C5ICAxUAIpsrOOHXaVAt4A"} 

read_jwk(jwk)

 [1] 0b 92 02 03 15 00 22 9b 2b 38 e1 d7 69 50 2d e0