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": "VrrkLu5GZsfqALTuLVXovBVOeKoiOaNbtOqZEwveg2U",
    "y": "7WR6wQFsGngrlhYhmMldJOxZc9obXJsdzWQe6MBHTls",
    "d": "Z7Z_7xUJj_GWMYXcPEzcDm2nlMDTm49UScLksn3gyM4"
}
 

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "VrrkLu5GZsfqALTuLVXovBVOeKoiOaNbtOqZEwveg2U",
    "y": "7WR6wQFsGngrlhYhmMldJOxZc9obXJsdzWQe6MBHTls"
}
 

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

[256-bit ecdsa public key]
md5: 512fb553be3149467d0b91b276e8c89d
sha256: 6a3ec63690afa7c552561fec3f6de65458f97b4135020b1bb4381a6dcbd229e2

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] ca 10 c4 e1 3c bb 86 f1 5a eb d1 2e ee 66 d1 fe

(jwk <- write_jwk(key))

{"kty":"oct","k":"yhDE4Ty7hvFa69Eu7mbR_g"} 

read_jwk(jwk)

 [1] ca 10 c4 e1 3c bb 86 f1 5a eb d1 2e ee 66 d1 fe