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86a6d1f9b4
Updated with new information since des3 and dsa are not recommended algorithms. Reviewed-by: Paul Dale <ppzgs1@gmail.com> Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/27343)
107 lines
3.6 KiB
Plaintext
107 lines
3.6 KiB
Plaintext
<DRAFT!>
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HOWTO keys
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1. Introduction
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Keys are the basis of public key algorithms and PKI. Keys usually
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come in pairs, with one half being the public key and the other half
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being the private key. With OpenSSL, the private key contains the
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public key information as well, so a public key doesn't need to be
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generated separately.
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Public keys come in several flavors, using different cryptographic
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algorithms. The most popular ones associated with certificates are
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RSA and ECDSA, and this HOWTO will show how to generate each of them.
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2. To generate an RSA key
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An RSA key can be used both for encryption and for signing.
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Generating a key for the RSA algorithm is quite easy, all you have to
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do is the following:
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openssl genrsa -aes256 -out privkey.pem 2048
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With this variant, you will be prompted for a protecting password. If
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you don't want your key to be protected by a password, remove the flag
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'-aes256' from the command line above.
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The number 2048 is the size of the key, in bits. Today, 2048 or
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higher is recommended for RSA keys, as fewer amount of bits is
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considered to be insecure.
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3. To generate an EC key
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An EC key can be used for either key agreement (ECDH), signing (ECDSA) or
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key encapsulation (KEM) purposes.
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(A key should only be used for one of these purposes)
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An EC key can be generated by specifying a curve name such as P-256 using:
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openssl genpkey -algorithm EC -pkeyopt group:P-256 -aes256 -out private.key
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With this variant, you will be prompted for a password to protect your key.
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If you don't want your key to be protected by a password, remove the flag
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'-aes256' from the command line above.
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Each curve name is associated with a group of fixed parameters.
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Curve names containing numbers lower than 256 are no longer considered
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secure.
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The NIST P-256 curve name (which is an alias for prime256v1), stands for
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'X9.62/SECG curve over a 256-bit prime field'.
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4. To generate a X25519 or X448 Key for Key Agreement
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X25519, X448, Ed25519 and Ed448 are treated as distinct algorithms and not as
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one of the EC curves listed with 'ecparam -list_curves' option.
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Unlike other algorithms there are separate key types for signing and
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key agreement.
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You can use the following command to generate an X25519 key:
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openssl genpkey -algorithm X25519 -out xkey.pem
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5. To generate a Ed25519 or Ed448 Key
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An Ed25519 or Ed448 key can be used for signing and verification purposes.
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You can use the following command to generate an Ed25519 key:
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openssl genpkey -algorithm Ed25519 -out xkey.pem
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6. To generate an ML-DSA key
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An ML-DSA key can be used for signing (and verification via the public key)
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only.
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Generating a key for the ML-DSA algorithm is a one-step process.
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openssl genpkey -algorithm ML-DSA-44 -out key.pem
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openssl genpkey -algorithm ML-DSA-65 -out key.pem
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openssl genpkey -algorithm ML-DSA-87 -out key.pem
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See L<EVP_PKEY-ML-DSA(7)> for more detail.
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7. To generate an ML-KEM key
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An ML-KEM key can be used for decapsulation (and encapsulation via the public
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key) only.
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Generating a key for the ML-KEM algorithm is a one-step process.
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openssl genpkey -algorithm ML-KEM-512 -out key.pem
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openssl genpkey -algorithm ML-KEM-768 -out key.pem
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openssl genpkey -algorithm ML-KEM-1024 -out key.pem
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See L<EVP_PKEY-ML-KEM(7)> for more detail.
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8. NOTE
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If you intend to use the key together with a server certificate,
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it may be reasonable to avoid protecting it with a password, since
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otherwise someone would have to type in the password every time the
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server needs to access the key.
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To generate keys using C code refer to the demos located in
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https://github.com/openssl/openssl/blob/master/demos/pkey.
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