NAME
    rsautl - RSA utility

SYNOPSIS
    openssl rsautl [-in file] [-out file] [-inkey file] [-pubin] [-certin]
    [-sign] [-verify] [-encrypt] [-decrypt] [-pkcs] [-ssl] [-raw] [-hex-
    dump] [-asn1parse]

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

COMMAND OPTIONS
    -in filename
   This specifies the input filename to read data from or standard
   input if this option is not specified.

    -out filename
   specifies the output filename to write to or standard output by
   default.

    -inkey file
   the input key file, by default it should be an RSA private key.

    -pubin
   the input file is an RSA public key.

    -certin
   the input is a certificate containing an RSA public key.

    -sign
   sign the input data and output the signed result. This requires and
   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, -ssl, -raw
   the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP, special
   padding used in SSL v2 backwards compatible handshakes, or no
   padding, respectively. For signatures, only -pkcs and -raw can be
   used.

    -hexdump
   hex dump the output data.

    -asn1parse
   asn1parse the output data, this is useful when combined with the
   -verify option.

NOTES
    rsautl because it uses the RSA algorithm directly can only be used to
    sign or verify small pieces of data.

EXAMPLES
    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 file -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 sec-
    ond byte) and random padding data visible instead of the 0xff bytes.

    It is possible to analyse the signature of certificates using this
    utility in conjunction with asn1parse. Consider the self signed example
    in certs/pca-cert.pem . Running asn1parse 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 -pubout -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
   dgst(1),rsa(1),genrsa(1)