Free Knowledge Resources


Linux Manual Pages


Free Software * Books

Source Code

Free Media

Linux

rsautl(1ssl)

NAME

   rsautl - RSA utility

SYNOPSIS

   openssl rsautl [-in file] [-out file] [-inkey file] [-pubin] [-certin]
   [-sign] [-verify] [-encrypt] [-decrypt] [-pkcs] [-ssl] [-raw]
   [-hexdump] [-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
   second 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 -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

   dgst(1), rsa(1), genrsa(1)



Opportunity


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.


Free Software


Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.


Free Books


The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Education


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.


birds banner