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": "o3IORxSyiATK8O0TlLhl0wDILCN48Mlvx4N1pLcCgLE",
    "y": "JUIrPIbCQtGT652jIPpsXIkClWrtojxi80w10fGtCc8",
    "d": "3Pz4jerMshoG0V8-6eTheBybaVYR4-I4Lj3V6UMJTnU"
}
 

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

{
    "kty": "EC",
    "crv": "P-256",
    "x": "o3IORxSyiATK8O0TlLhl0wDILCN48Mlvx4N1pLcCgLE",
    "y": "JUIrPIbCQtGT652jIPpsXIkClWrtojxi80w10fGtCc8"
}
 

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

[256-bit ecdsa public key]
md5: f7279e786da2ad52164a8ffd5bd1a37f
sha256: 0269375eb2bac4a4d37ac14850ace73ed5954824882ffc0704f0dc0ee31aad44

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] b9 d3 12 95 4d 76 dc ab 1e db d5 3f f2 f3 17 25

(jwk <- write_jwk(key))

{"kty":"oct","k":"udMSlU123Kse29U_8vMXJQ"} 

read_jwk(jwk)

 [1] b9 d3 12 95 4d 76 dc ab 1e db d5 3f f2 f3 17 25