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 1.1.1h  22 Sep 2020

library(jose)

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "4mRfH_XLZK3kDAgKcsUWrowDVwMbJu1cLe4Lp2qG4vk",
    "y": "V8lFNwC6XPL9HWla-IT1Tea_dQKJXVsDYe0ezfv_RCI",
    "d": "x9VXjILw4gNU9LID1pKNkvGXKq8tCS0m4asW5rbsCe0"
}
 

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "4mRfH_XLZK3kDAgKcsUWrowDVwMbJu1cLe4Lp2qG4vk",
    "y": "V8lFNwC6XPL9HWla-IT1Tea_dQKJXVsDYe0ezfv_RCI"
}
 

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

[256-bit ecdsa public key]
md5: 01965264c60f4a699503498ab348735c

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] 1a a9 b7 c3 e1 f7 cc eb 60 1b f6 fe 4c f5 5d 91

(jwk <- write_jwk(key))

{"kty":"oct","k":"Gqm3w-H3zOtgG_b-TPVdkQ"} 

read_jwk(jwk)

 [1] 1a a9 b7 c3 e1 f7 cc eb 60 1b f6 fe 4c f5 5d 91