The openssl
package implements a modern
interface to libssl and libcrypto for R. It builds on the new
EVP
api which was introduced in OpenSSL 1.0 and provides a
unified API to the various methods and formats. OpenSSL supports three
major public key crypto systems:
For each type there are several common formats for storing keys and certificates:
===
The openssl package automatically detects the format when possible. However being able to recognize the various formats can be useful.
DER is the standard binary format using by protocols for storing and exchanging keys and certificates. It consists of a serialized ASN.1 structure which hold the key’s (very large) prime numbers.
[1] 30 59 30 13 06 07 2a 86 48 ce 3d 02 01 06 08 2a 86 48 ce 3d 03 01 07 03 42
[26] 00 04 f4 70 7d c9 18 5f 02 97 db 15 0e 7e bc 6b d8 e2 fb d8 9f 33 7b d7 dd
[51] f7 70 e4 77 d2 13 13 ed 7a 2c ac 65 15 90 3a 1a 0b e1 b2 f4 b1 45 37 18 0c
[76] 66 54 73 6d 56 16 15 df 08 2c 7a 26 9d 45 17 42
To read a DER key use read_key
or
read_pubkey
with der = TRUE
.
[256-bit ecdsa public key]
md5: 60cff0fc85149d53fbcb0c443823c16b
sha256: bce8e5c9925f71d85157cb8c3b171116b0d8f67cebca7c1d865303e74bac1e5c
Users typically don’t need to worry about the key’s underlying
primes, but have a look at key$data
if you are curious.
In practice the user rarely encounters DER because it is mainly for internal use. When humans exchange keys and certificates they typically use the PEM format. PEM is simply base64 encoded DER data, plus a header. The header identifies the key (and possibly encryption) type.
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE9HB9yRhfApfbFQ5+vGvY4vvYnzN7
1933cOR30hMT7XosrGUVkDoaC+Gy9LFFNxgMZlRzbVYWFd8ILHomnUUXQg==
-----END PUBLIC KEY-----
-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgQUEJMHEZXONaRAFM
oEyKBOP7Gb6Y1xUJBsq5R5vENjqhRANCAAT0cH3JGF8Cl9sVDn68a9ji+9ifM3vX
3fdw5HfSExPteiysZRWQOhoL4bL0sUU3GAxmVHNtVhYV3wgseiadRRdC
-----END PRIVATE KEY-----
The PEM format allows for protecting private keys with a password. R will prompt you for the password when reading such a protected key.
-----BEGIN ENCRYPTED PRIVATE KEY-----
MIHjME4GCSqGSIb3DQEFDTBBMCkGCSqGSIb3DQEFDDAcBAhV3u9RT33m7QICCAAw
DAYIKoZIhvcNAgkFADAUBggqhkiG9w0DBwQIb35bxztnz28EgZAF5dCPzXhSGOLv
PXtgmmm9GEg9oqaXFGQUS7Powt17cjW0xcbrooPPvdLDgWafHy7ro2+Dz0Cf78Kt
meS1DSx21POmbNB/Swdjr5MuRbeHxr8jioTzgCGlSjDKc/AgNa3zXQk3CHbGiZnZ
HE7vdrF1jdXrpXracvaXAIzzgP/+RD9BicCThl88UrIGmFcyy9c=
-----END ENCRYPTED PRIVATE KEY-----
For better or worse, OpenSSH uses a custom format for public
keys. The advantage of this format is that it fits on a single
line which is nice for e.g. your ~/.ssh/known_hosts
file.
There is no special format for private keys, OpenSSH uses PEM as
well.
[1] "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBPRwfckYXwKX2xUOfrxr2OL72J8ze9fd93Dkd9ITE+16LKxlFZA6GgvhsvSxRTcYDGZUc21WFhXfCCx6Jp1FF0I="
The read_pubkey
function will automatically detect if a
file contains a PEM
or SSH
key.
[256-bit ecdsa public key]
md5: 60cff0fc85149d53fbcb0c443823c16b
sha256: bce8e5c9925f71d85157cb8c3b171116b0d8f67cebca7c1d865303e74bac1e5c
Yet another recent format to store RSA or EC keys are JSON Web Keys
(JWK). JWK is part of the Javascript Object Signing and
Encryption (JOSE) specification. The write_jwk
and
read_jwk
functions are implemented in a separate package
which uses the openssl
package.
{
"kty": "EC",
"crv": "P-256",
"x": "9HB9yRhfApfbFQ5-vGvY4vvYnzN71933cOR30hMT7Xo",
"y": "LKxlFZA6GgvhsvSxRTcYDGZUc21WFhXfCCx6Jp1FF0I"
}
Keys from jose
and openssl
are the
same.
[1] TRUE
[256-bit ecdsa public key]
md5: 60cff0fc85149d53fbcb0c443823c16b
sha256: bce8e5c9925f71d85157cb8c3b171116b0d8f67cebca7c1d865303e74bac1e5c