OPENSSL-RSAUTL(1) | OpenSSL | OPENSSL-RSAUTL(1)

# NAME

openssl-rsautl - RSA command

# SYNOPSIS

openssl rsautl [-help] [-in file] [-passin arg] [-rev] [-out file] [-inkey filename|uri] [-keyform DER|PEM|P12|ENGINE] [-pubin] [-certin] [-sign] [-verify] [-encrypt] [-decrypt] [-pkcs] [-x931] [-oaep] [-raw] [-hexdump] [-asn1parse] [-engine id] [-rand files] [-writerand file] [-provider name] [-provider-path path] [-provparam [name:]key=value] [-propquery propq]

# DESCRIPTION

This command has been deprecated. The openssl-pkeyutl(1) command should be used instead.

This command can be used to sign, verify, encrypt and decrypt data using the RSA algorithm.

# OPTIONS

-help
  Print out a usage message.
-in filename
  This specifies the input filename to read data from or standard input if this option is not specified.
-passin arg
  The passphrase used in the output file. See see openssl-passphrase-options(1).
-rev
  Reverse the order of the input.
-out filename
  Specifies the output filename to write to or standard output by default.
-inkey filename|uri
  The input key, by default it should be an RSA private key.
-keyform DER|PEM|P12|ENGINE
  The key format; unspecified by default. See openssl-format-options(1) for details.
-pubin
  By default a private key is read from the key input. With this option a public key is read instead. If the input contains no public key but a private key, its public part is used.
-certin
  The input is a certificate containing an RSA public key.
-sign
  Sign the input data and output the signed result. This requires an RSA private key.
-verify
  Verify the input data and output the recovered data.
-encrypt
  Encrypt the input data using an RSA public key.
-decrypt
  Decrypt the input data using an RSA private key.
-pkcs, -oaep, -x931, -raw
  The padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP, ANSI X9.31, or no padding, respectively. For signatures, only -pkcs and -raw can be used.

  Note: because of protection against Bleichenbacher attacks, decryption using PKCS#1 v1.5 mode will not return errors in case padding check failed. Use -raw and inspect the returned value manually to check if the padding is correct.

-hexdump
  Hex dump the output data.
-asn1parse
  Parse the ASN.1 output data, this is useful when combined with the -verify option.
-engine id
  See "Engine Options" in openssl(1). This option is deprecated.
-rand files, -writerand file
  See "Random State Options" in openssl(1) for details.
-provider name
-provider-path path
-provparam [name:]key=value
-propquery propq
  See "Provider Options" in openssl(1), provider(7), and property(7).

# NOTES

Since this command uses the RSA algorithm directly, it can only be used to sign or verify small pieces of data.

# EXAMPLES

Examples equivalent to these can be found in the documentation for the non-deprecated openssl-pkeyutl(1) command.

Sign some data using a private key:

     openssl rsautl -sign -in file -inkey key.pem -out sig

Recover the signed data

     openssl rsautl -verify -in sig -inkey key.pem

Examine the raw signed data:

     openssl rsautl -verify -in sig -inkey key.pem -raw -hexdump
     0000 - 00 01 ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0010 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0020 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0030 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0040 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0050 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0060 - ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff   ................
     0070 - ff ff ff ff 00 68 65 6c-6c 6f 20 77 6f 72 6c 64   .....hello world

The PKCS#1 block formatting is evident from this. If this was done using encrypt and decrypt the block would have been of type 2 (the second byte) and random padding data visible instead of the 0xff bytes.

It is possible to analyse the signature of certificates using this command in conjunction with openssl-asn1parse(1). Consider the self signed example in certs/pca-cert.pem. Running openssl-asn1parse(1) as follows yields:

     openssl asn1parse -in pca-cert.pem
        0:d=0  hl=4 l= 742 cons: SEQUENCE
        4:d=1  hl=4 l= 591 cons:  SEQUENCE
        8:d=2  hl=2 l=   3 cons:   cont [ 0 ]
       10:d=3  hl=2 l=   1 prim:    INTEGER           :02
       13:d=2  hl=2 l=   1 prim:   INTEGER           :00
       16:d=2  hl=2 l=  13 cons:   SEQUENCE
       18:d=3  hl=2 l=   9 prim:    OBJECT            :md5WithRSAEncryption
       29:d=3  hl=2 l=   0 prim:    NULL
       31:d=2  hl=2 l=  92 cons:   SEQUENCE
       33:d=3  hl=2 l=  11 cons:    SET
       35:d=4  hl=2 l=   9 cons:     SEQUENCE
       37:d=5  hl=2 l=   3 prim:      OBJECT            :countryName
       42:d=5  hl=2 l=   2 prim:      PRINTABLESTRING   :AU
      ....
      599:d=1  hl=2 l=  13 cons:  SEQUENCE
      601:d=2  hl=2 l=   9 prim:   OBJECT            :md5WithRSAEncryption
      612:d=2  hl=2 l=   0 prim:   NULL
      614:d=1  hl=3 l= 129 prim:  BIT STRING

The final BIT STRING contains the actual signature. It can be extracted with:

     openssl asn1parse -in pca-cert.pem -out sig -noout -strparse 614

The certificate public key can be extracted with:

     openssl x509 -in test/testx509.pem -pubkey -noout >pubkey.pem

The signature can be analysed with:

     openssl rsautl -in sig -verify -asn1parse -inkey pubkey.pem -pubin
        0:d=0  hl=2 l=  32 cons: SEQUENCE
        2:d=1  hl=2 l=  12 cons:  SEQUENCE
        4:d=2  hl=2 l=   8 prim:   OBJECT            :md5
       14:d=2  hl=2 l=   0 prim:   NULL
       16:d=1  hl=2 l=  16 prim:  OCTET STRING
          0000 - f3 46 9e aa 1a 4a 73 c9-37 ea 93 00 48 25 08 b5   .F...Js.7...H%..

This is the parsed version of an ASN1 DigestInfo structure. It can be seen that the digest used was md5. The actual part of the certificate that was signed can be extracted with:

     openssl asn1parse -in pca-cert.pem -out tbs -noout -strparse 4

and its digest computed with:

     openssl md5 -c tbs
     MD5(tbs)= f3:46:9e:aa:1a:4a:73:c9:37:ea:93:00:48:25:08:b5

which it can be seen agrees with the recovered value above.

# SEE ALSO

openssl(1), openssl-pkeyutl(1), openssl-dgst(1), openssl-rsa(1), openssl-genrsa(1)

# HISTORY

This command was deprecated in OpenSSL 3.0.

The -engine option was deprecated in OpenSSL 3.0.

# COPYRIGHT

Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

2025-07-18 | 3.5.1