Loading and Managing System Images Configuration Guide, Cisco IOS Release 15S
Digitally Signed Cisco Software
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Digitally Signed Cisco Software

Contents

Digitally Signed Cisco Software

The Digitally Signed Cisco Software feature describes how to identify digitally signed Cisco software, gather software authentication information related to digitally signed images, and perform key revocation. Digitally Signed Cisco software is software that is digitally signed using secure asymmetrical (public-key) cryptography.

The purpose of digitally signed Cisco software is to ensure that customers are confident that the software running within their systems is secure and has not been tampered with, and that the software running in those systems originated from the trusted source as claimed.

For customers concerned about software updates involving digitally signed Cisco software--no action is necessary for customers to take advantage of the increased protection. The system operation is largely transparent to existing practices. Some minor changes in system displays reflect the use of digitally signed Cisco software.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Restrictions for Digitally Signed Cisco Software

The Cisco 19xx Series, 29xx, and 39xx series routers include the functionality described in this document.

The Cisco Catalyst 4500 E+Series switches running IOS XE software and the Cisco ASR 1002-X Router include the functionality described in this document, except for Digitally Signed Software Key Revocation and Replacement.

Information About Digitally Signed Cisco Software

Features and Benefits of Digitally Signed Cisco Software

Three main factors drive digitally signed Cisco software and software integrity verification:

  • The U.S. government is introducing a new version of the Federal Information Processing Standard (FIPS) 140. FIPS-140-3 is the latest draft and is scheduled for ratification in 2010 and to be effective in 2011. This standard requires software to be digitally signed and to be verified for authenticity and integrity prior to load and execution.
  • The focus on product security provides increased protection from attacks and threats to Cisco products. Digitally signed Cisco software offers increased protection from the installation and loading of software that has been corrupted or modified.
  • Digitally signed Cisco software provides counterfeit protection, which provides further assurance for customers that the equipment they purchase is as claimed.

Digitally Signed Cisco Software Identification

Digitally signed Cisco IOS software is identified by a three-character extension in the image name. The Cisco software build process creates a Cisco IOS image file that contains a file extension based on the signing key that was used to sign images. These file extensions are:

  • .SPA
  • .SSA

The significance of each character in the file extension is explained in the table below.

Table 1 Digitally Signed Cisco Software Images File Extension Character Meanings

File Extension Character

Character Meaning

S (first character)

Stands for digitally signed software.

P or S (second character)

P and S stand for a production and special (development) image, respectively. A production image is Cisco software approved for general release; a special image is development software provided under special conditions for limited use.

A (third character)

Indicates the key version used to digitally sign the image. A key version is identified by an alphabetical character - for example, A,B,C...

Digitally Signed Cisco Software Key Types and Versions

Digitally signed Cisco software keys are identified by the type and version of the key. A key can be a special, production, or rollover key type. Special and production keys can be revoked. A rollover key is used to revoke a production or special key. The second character in the file extension indicates whether the key type is a special or production key. The key type can be “P” for a production key or an “S” for a special key.

Production and special key types have an associated key version. The key version is defined by the third character in the file extension, in the form of an alphabetical character; for example A, B or C. When a key is replaced, the key version is incremented alphabetically. For example, after a key revocation of a key type “P” (production key) with a key version of “A”, the new image will be signed with key version “B”. Key type and key version are stored as part of the key record in the key storage of the router.

Digitally Signed Cisco Software Key Revocation and Replacement


Note


Key revocation and replacement is not supported on Catalyst 4500 E+Series switches running IOS XE software.


Key Revocation

Key revocation is the process of removing a key from operational use in digitally signed Cisco software.

Key revocation takes place when a key becomes compromised or is no longer used. Key revocation and replacement is only necessary in the event of a certain type of vulnerability or catastrophic loss to Cisco's secure key infrastructure. Operational steps to remedy the situation would only be necessary if notified and directed by Cisco. Notification and direction would occur through posting of advisories or field notices on www.cisco.com.

There are two different key revocation processes depending on the type of key to be revoked:

  • Production key replacement uses a revocation image and a production image
  • Special key replacement uses a production image

Key Replacement

Key replacement is the process of providing a new key to replace a compromised key. The new key is added before the compromised key is revoked. Key replacement is a two-step process:

  1. A new key is added to the key storage to replace the revoked key.
  2. After the image is verified as operating correctly with the new key, the compromised key is revoked from the key storage.

Key Revocation Image

A revocation image is a basic version of the normal image whose function is to add a new production key to the key storage area. A revocation image has no other capabilities. When a key is to be revoked and replaced, one revocation image per key is provided.

A revocation image contains a new production key bundled within it.

A rollover key stored on the platform is used to verify the signature of the revocation image--a valid revocation image is signed using the same rollover key.


Note


A revocation image can be used only in production key revocation.


Important Tasks Concerning the Revocation Image

There are two important tasks concerning the revocation image:

  • Adding the new production key to the key storage area.
  • Performing a production key upgrade check. For more information, see Step 2 in the “Production Key Revocation”.
Adding the New Production Key to the Key Storage Area:

The revocation image adds the bundled production key to the key storage. The key is written to the primary and backup key storage areas after the revocation image checks that the key is already not part of the existing set of keys in the key storage.

Performing a Key Upgrade Check:

After the new key is added and the customer has upgraded the software (Cisco IOS and ROMmon), the show software authenticity upgrade-status command should be run. The user can review the command output to determine if the production key is successfully upgraded, and can be selected for the next boot.

Production Key Revocation

A production key (also called the release key) is revoked and replaced using a revocation image signed with a rollover key, because the images signed using the compromised production key cannot be trusted. The ROMmon can boot any image signed using a rollover key. The production key revocation and replacement process involves four steps:

  1. Add the new production key to the key storage. The new production key is bundled within the revocation image.
  2. Perform a software upgrade check using the show software authenticity upgrade-status command to verify the following:
    • The new production key version is installed.
    • The new production key is added to the primary key storage (if not, issue the software authenticity key add production command again with the existing revocation image).
    • The new production key is added to the backup key storage (if not, issue the software authenticity key add production command again with the existing revocation image).
    • The image is configured for autoboot (with the boot system command) signed with the new production key (if not, make sure the new production image is copied into the box and modify the boot system command to point to the new image).
    • The upgradable ROMmon is signed with the new production key (if not, upgrade the ROMmon to the one signed with the new production key).
  3. Once everything is verified, the user may load the production image signed with the new production key by using the reload command.
  4. Once the new production image is loaded, the user may revoke the compromised key using the software authenticity key revoke production command.

Steps 1 and 2 are done using the special revocation image. It is important for the user to do verifications in Step 2 because after a reboot (in Step 3), an old key will not be revoked if any of the software is still using the old key. The verifications help to ensure that the new key is fully installed and the next reboot (in Step 3) will use the new release software and new ROMmon. Revoking the old production key (Step 4) can be done only after the new key and the new software are installed to the system.

Special Key Revocation

A special key is revoked using a production image signed with a production key. Each production image used for special key revocation has a bundled special key that is the latest at the time of building the production image. The special key revocation and replacement process involves three steps:

  1. Add the bundled new special key to the key storage area.
  2. Upgrade the ROMmon that is signed using the compromise special key, to the new ROMmon signed with the new special key.
  3. Revoke the compromised key from the key storage.

Note that Step 3 does not require any reboot and will be done using the production image itself. This is because the customer is already running a production image and invalidation itself happens from the running production image. Special images do not have the capability to add or invalidate any key.

How to Work with Digitally Signed Cisco Software Images

Identifying Digitally Signed Cisco Software

Perform this task to identify digitally signed Cisco software by examining the image filename in the command output from the show version command, and judging it on the criteria described in the “Digitally Signed Cisco Software Identification” section.


Note


If the image file has been renamed by the user, it may not be possible to identify the image because the user may have overwritten the criteria used to indicate that the image is digitally signed.


SUMMARY STEPS

    1.    enable

    2.    show version


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 show version


    Example:
    Router# show version
     

    Displays information about the Cisco IOS software version running on a routing device, the ROM Monitor and Bootflash software versions, and the hardware configuration, including the amount of system memory.

     

    Displaying Digitally Signed Cisco Software Signature Information

    Perform this task to display information related to software authentication for the current ROMmon and the Cisco IOS image file used for booting. The display includes image credential information, the key type used for verification, signature information, and other attributes in the signature envelope.

    SUMMARY STEPS

      1.    enable

      2.    show software authenticity running


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 show software authenticity running


      Example:
      Router# show software authenticity running
       

      Displays software authenticity-related information for the current ROMmon and the Cisco IOS image file used for booting.

       

      Displaying Digital Signature Information for a Specific Image File

      Perform this task to display the digital signature information related to software authentication for a specific image file.

      SUMMARY STEPS

        1.    enable

        2.    show software authenticity file {flash0:filename | flash1:filename | flash:filename | nvram:filename | usbflash0:filename | usbflash1:filename}


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 show software authenticity file {flash0:filename | flash1:filename | flash:filename | nvram:filename | usbflash0:filename | usbflash1:filename}


        Example:
        Router# show software authenticity file usbflash0:c3900-universalk9-mz.SPA
         

        Displays digital signature and software authenticity-related information for a specific image file.

         

        Displaying Digitally Signed Cisco Software Key Information

        Perform this task to display digitally signed Cisco software key information. The information details the software public keys that are in storage with the key types.

        SUMMARY STEPS

          1.    enable

          2.    show software authenticity keys


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 show software authenticity keys


          Example:
          Router# show software authenticity keys
           

          Displays the software public keys that are in storage with the key types for digitally signed Cisco software.

           

          Performing Production Key Revocation for Digitally Signed Cisco Software

          Perform this task to perform production key revocation for digitally signed Cisco software.

          Before You Begin

          This task must be performed with a dedicated revocation image.

          SUMMARY STEPS

            1.    enable

            2.    sof tware authenticity key add production

            3.    show sof tware authenticity upgrade-status

            4.    copy [/erase] [/verify | /noverify] source-urldestination-url

            5.    copy [/erase] [/verify | /noverify] source-urldestination-url

            6.    upgrade rom-monitor file {archive: | cns: | flash0: | flash1: | flash: | ftp: | http: | https: | null: | nvram: | rcp: | scp: | system: | tar: | tftp: | tmpsys: | usbflash0: | xmodem: | ymodem:} [file-path]

            7.    reload [/verify | /noverify] [line | in [hhh:mm | mmm [text]] | at hh:mm [text] | reason [reason string] | cancel]

            8.    sof tware authenticity key revoke production


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Router> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 sof tware authenticity key add production


            Example:
            Router# software authenticity key add production
             

            Adds the bundled production key to the key storage of a router with digitally signed Cisco software when run from a revocation image.

            • An error message will be displayed if this command is used with a special or production image.
             
            Step 3 show sof tware authenticity upgrade-status


            Example:
            Router# show software authenticity upgrade-status
             

            Displays software authentication upgrade-status information about the Cisco IOS digitally signed image file and the ROMMON file.

             
            Step 4 copy [/erase] [/verify | /noverify] source-urldestination-url


            Example:
            Router# copy tftp: usbflash0:
             

            Copies an image from a TFTP server to the selected router storage area.

            • The new production ROMmon image signed with a new production key is copied to the selected router storage with this command.
             
            Step 5 copy [/erase] [/verify | /noverify] source-urldestination-url


            Example:
            Router# copy /verify tftp: usbflash0:
             

            Copies an image from a TFTP server to the selected router storage area.

            • The new production image signed with a new production key is copied to the selected router storage with this command.
            • It is recommended to use the /verify option in order to verify the signature of the new image during the copy process.
             
            Step 6 upgrade rom-monitor file {archive: | cns: | flash0: | flash1: | flash: | ftp: | http: | https: | null: | nvram: | rcp: | scp: | system: | tar: | tftp: | tmpsys: | usbflash0: | xmodem: | ymodem:} [file-path]


            Example:
            Router# upgrade rom-monitor file flash0:C3900_ROMMON_RM2.srec.SPB
             

            Upgrades the ROM monitor (ROMMON) image.

             
            Step 7 reload [/verify | /noverify] [line | in [hhh:mm | mmm [text]] | at hh:mm [text] | reason [reason string] | cancel]

            Example:
            Router# reload
             

            Reloads the software on the router.

            Note   

            The warm upgrade functionality does not support key revocation.

             
            Step 8 sof tware authenticity key revoke production


            Example:
            Router# software authenticity key revoke production
             

            Revokes or invalidates the old production key from the key storage when run from a production image.

            • An error message will be displayed if this command is used with a special image.
            Note   

            This step must be performed after the reload is complete. It is important to be aware of this in the event of a scheduled reload.

             

            Performing Special Key Revocation for Digitally Signed Cisco Software

            Perform this task to perform special key revocation for digitally signed Cisco software.

            Before You Begin

            This task must be performed with a production image.

            SUMMARY STEPS

              1.    enable

              2.    sof tware authenticity key add special

              3.    copy [/erase] [/verify | /noverify] source-urldestination-url

              4.    copy [/erase] [/verify | /noverify] source-urldestination-url

              5.    upgrade rom-monitor file {archive: | cns: | flash0: | flash1: | flash: | ftp: | http: | https: | null: | nvram: | rcp: | scp: | system: | tar: | tftp: | tmpsys: | usbflash0: | xmodem: | ymodem:} [file-path]

              6.    sof tware authenticity key revoke special


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 sof tware authenticity key add special


              Example:
              Router# software authenticity key add production
               

              Adds a new special key to the key storage area of a router loaded with digitally signed Cisco software.

              • An error message will be displayed if this command is used with a revocation or special image.

               
              Step 3 copy [/erase] [/verify | /noverify] source-urldestination-url


              Example:
              Router# copy tftp: usbflash0:
               

              Copies an image from a TFTP server to the selected router storage area.

              • The new special ROMmon image signed with a new special key is copied to the selected router storage area in this line.
               
              Step 4 copy [/erase] [/verify | /noverify] source-urldestination-url


              Example:
              
              
                      


              Example:
              
              
                      


              Example:
              
              
                      


              Example:
              Router# copy /verify tftp: usbflash0:
               

              Copies an image from a TFTP server to the selected router storage area.

              • The new special image signed with a new special key is copied to the selected router storage area in this line.
              • It is recommended to use the /verify option in order to verify the signature of the new image during the copy process.
               
              Step 5 upgrade rom-monitor file {archive: | cns: | flash0: | flash1: | flash: | ftp: | http: | https: | null: | nvram: | rcp: | scp: | system: | tar: | tftp: | tmpsys: | usbflash0: | xmodem: | ymodem:} [file-path]


              Example:
              Router# upgrade rom-monitor file flash0:C3900_ROMMON_RM2.srec.SSB
               

              Upgrades the ROM monitor (ROMmon) image in privileged EXEC mode.

               
              Step 6 sof tware authenticity key revoke special


              Example:
              Router# software authenticity key revoke special
               

              Revokes or invalidates the old special key from the key storage when run from a production image.

              • An error message will be displayed if run from a special or revocation image.
               

              Troubleshooting Digitally Signed Cisco Software Images

              Perform this task to troubleshoot digitally signed Cisco software images.

              SUMMARY STEPS

                1.    enable

                2.    debug software authenticity {envelope | errors | key | revocation | show | verbose}


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example:
                Router> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.
                 
                Step 2 debug software authenticity {envelope | errors | key | revocation | show | verbose}


                Example:
                Router# debug software authenticity errors
                 

                Enables the display of debug messages for digitally signed Cisco software.

                 

                Configuration Examples for Digitally Signed Cisco Software

                Identifying Digitally Signed Cisco Software Example

                The following example displays the digitally signed Cisco software image filename and allows a user to identify it based on the digitally signed Cisco software identification criteria:

                Router# show version
                Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), 
                12.4(20090904:044027) [i12 577]
                Copyright (c) 1986-2009 by Cisco Systems, Inc.
                Compiled Fri 04-Sep-09 09:22 by xxx
                ROM: System Bootstrap, Version 12.4(20090303:092436) 
                C3900-2 uptime is 8 hours, 41 minutes
                System returned to ROM by reload at 08:40:40 UTC Tue May 21 1901! 
                System image file is "xxx.SPA"
                Last reload reason: Reload Command
                This product contains cryptographic features and is subject to United
                States and local country laws governing import, export, transfer and
                use. Delivery of Cisco cryptographic products does not imply
                third-party authority to import, export, distribute or use encryption.
                Importers, exporters, distributors and users are responsible for
                compliance with U.S. and local country laws. By using this product you
                agree to comply with applicable laws and regulations. If you are unable
                to comply with U.S. and local laws, return this product immediately.
                          
                A summary of U.S. laws governing Cisco cryptographic products may be found at:
                http://www.cisco.com/wwl/export/crypto/tool/stqrg.html
                If you require further assistance please contact us by sending email to
                export@cisco.com.
                Cisco xxx (revision 1.0) with CISCxxx with 987136K/61440K bytes of memory.
                Processor board ID xxx
                3 Gigabit Ethernet interfaces
                1 terminal line
                1 Virtual Private Network (VPN) Module
                1 cisco Integrated Service Engine(s)
                DRAM configuration is 72 bits wide with parity enabled.
                255K bytes of non-volatile configuration memory.
                1020584K bytes of USB Flash usbflash0 (Read/Write)
                1020584K bytes of USB Flash usbflash1 (Read/Write)
                500472K bytes of ATA System CompactFlash 0 (Read/Write)
                License Info:
                License UDI:
                -------------------------------------------------
                Device#   PID                   SN
                -------------------------------------------------
                xx        xxx                   xxxx 
                Technology Package License Information for Module:'xxx' 
                ----------------------------------------------------------------
                Technology    Technology-package          Technology-package
                              Current       Type          Next reboot  
                -----------------------------------------------------------------
                ipbase        ipbasek9      Permanent     ipbasek9
                security      securityk9    Evaluation    securityk9
                uc            None          None          None
                data          None          None          None
                Configuration register is 0x2102
                

                Note the digitally signed image file is identified in the following line:

                System image file is "xxx.SPA"
                

                The image has a three-character extension in the filename (.SPA) characteristic of digitally signed Cisco software. Based on the guidelines in the “Digitally Signed Cisco Software Identification” section the first character in the file extension “S” indicates that the image is a digitally signed software image, the second character “P” indicates that the image is digitally signed using a production key, and the third character “A” indicates that the key version is version A.

                Displaying Digitally Signed Cisco Software Signature Information Example

                The following example shows how to display information related to software authentication for the current ROMmon and Cisco IOS image file used for booting:

                Router# show software authenticity running
                SYSTEM IMAGE
                -------------------
                Image type                    : Development
                    Signer Information
                        Common Name           : xxx
                        Organization Unit     : xxx
                        Organization Name     : xxx
                    Certificate Serial Number : xxx
                    Hash Algorithm            : xxx
                    Signature Algorithm       : 2048-bit RSA
                    Key Version               : xxx
                 
                    Verifier Information
                        Verifier Name         : ROMMON 2
                        Verifier Version      :  System Bootstrap, Version 12.4(20090409:084310) 
                ROMMON 2
                ---------------
                Image type                    : xxx
                    Signer Information
                        Common Name           : xxx
                        Organization Unit     : xxx
                        Organization Name     : xxx
                    Certificate Serial Number : xxx
                    Hash Algorithm            : xxx
                    Signature Algorithm       : 2048-bit RSA
                    Key Version               : xx
                 
                    Verifier Information
                        Verifier Name         : ROMMON 2
                        Verifier Version      :  System Bootstrap, Version 12.4(20090409:084310) [
                

                The table below describes the significant fields shown in the display.

                Table 2 show software authenticity running Field Descriptions

                Field

                Description

                SYSTEM IMAGE

                Section of the output displaying the system image information.

                Image type

                Displays the type of image.

                Common Name

                Displays the name of the software manufacturer.

                Organization Unit

                Displays the hardware the software image is deployed on.

                Organization Name

                Displays the owner of the software image.

                Certificate Serial Number

                Displays the certificate serial number for the digital signature.

                Hash Algorithm

                Displays the type of hash algorithm used in digital signature verification.

                Signature Algorithm

                Displays the type of signature algorithm used in digital signature verification.

                Key Version

                Displays the key version used for verification.

                Verifier Name

                Name of the program responsible for performing the digital signature verification.

                Verifier Version

                Version of the program responsible for performing the digital signature verification.

                ROMMON 2

                Section of the output displaying the current ROMmon information.

                Displaying the Digital Signature Information for a Specific Image File Example

                The following example shows how to display the digital signature information related to software authentication for a specific image file:

                Router# showsoftwareauthenticityfileflash0:c3900-universalk9-mz.SSA

                File Name                     : flash0:c3900-universalk9-mz.SSA 
                Image type                    : Development 
                    Signer Information 
                        Common Name           : xxx 
                        Organization Unit     : xxx 
                        Organization Name     : xxx 
                    Certificate Serial Number : xxx 
                    Hash Algorithm            : SHA512 
                    Signature Algorithm       : 2048-bit RSA 
                    Key Version               : A
                
                The table below describes the significant fields shown in the display.
                
                Table 3 show software authenticity file Field Descriptions

                Field

                Description

                File Name

                Name of the filename in the memory. For example, flash0:c3900-universalk9-mz.SSA refers to filename c3900-universalk9-mz.SSA in flash memory (flash0:).

                Image type

                Displays the type of image.

                Signer Information

                Signature information.

                Common Name

                Displays the name of the software manufacturer.

                Organization Unit

                Displays the hardware the software image is deployed on.

                Organization Name

                Displays the owner of the software image.

                Certificate Serial Number

                Displays the certificate serial number for the digital signature.

                Hash Algorithm

                Displays the type of hash algorithm used in digital signature verification.

                Signature Algorithm

                Displays the type of signature algorithm used in digital signature verification.

                Key Version

                Displays the key version used for verification.

                Displaying Digitally Signed Cisco Software Key Information Example

                The following example displays digitally signed Cisco software key information. The information details the software public keys that are in storage, including their key types.

                Router# show software authenticity keys
                Public Key #1 Information 
                ------------------------- 
                Key Type             : Release  (Primary) 
                Public Key Algorithm : RSA 
                Modulus : 
                        CC:CA:40:55:8C:71:E2:4A:3A:B6:9D:5C:94:1D:02:BA: 
                       ...
                        26:04:6B:33:EB:70:2B:18:24:C7:D9:31:3E:77:24:85 
                Exponent : xxx 
                Key Version          : A 
                Public Key #2 Information 
                ------------------------- 
                Key Type             : Development  (Primary) 
                Public Key Algorithm : RSA 
                Modulus :
                        CC:CA:40:55:8C:71:E2:4A:3A:B6:9D:5C:94:1D:02:BA: 
                       ....
                        26:04:6B:33:EB:70:2B:18:24:C7:D9:31:3E:77:24:85 
                Exponent : xxx 
                Key Version          : A 
                
                The table below describes the significant fields shown in the display.
                
                Table 4 show software authenticity keys Field Descriptions

                Field

                Description

                Public Key #

                Public key number.

                Key Type

                Displays the key type used for image verification.

                Public Key Algorithm

                Displays the name of the algorithm used for public key cryptography.

                Modulus

                Modulus of the public key algorithm.

                Exponent

                Exponent of the public key algorithm

                Key Version

                Displays the key version used for verification.

                Performing Special Key Revocation for Digitally Signed Cisco Software Example

                The following example displays a special key revocation process:

                Router# software authenticity key add special
                Validating running image...
                Validating new special key...
                Adding the key to Primary
                Checking for duplicate keys
                Writing the key...e.Success
                Adding the key to Backup
                Checking for duplicate keys
                Writing the key...e.Success
                Done!
                

                The software authenticity key add special command adds the new special key to the primary and backup storage areas of the router and verifies that a duplicate key is not present.

                Router# copy tftp: usbflash0:
                Address or name of remote host []? 209.165.200.226
                Source filename []? rommon_image_location/ C3900_rom-monitor.srec.SSB
                

                The new ROMmon special image file with a new special key is copied to the ROMmon storage area (usbflash0:).

                Router# copy /verify tftp: usbflash0:
                Address or name of remote host []? 209.165.200.225
                Source filename []? image_location/c3900-universalk9-mz.SSB
                Destination filename [c3900-universalk9-mz.SSB]? 
                Accessing tftp:// 209.165.200.225/image_location/c3900-universalk9-mz.SSB...
                Loading image_location/c3900-universalk9-mz.SSB from 209.165.200.225 (via GigabitEthernet0/0): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                [OK - 52291428 bytes]
                 
                52291428 bytes copied in 124.804 secs (418988 bytes/sec)
                 
                Starting image verification
                Hash Computation:    100% Done!
                Computed Hash   SHA2: 7F54083493EB6B06234CFC5266E538E7
                                      .....
                                      .....
                                      0B17572E9A33735ADCEE26A4E3FDB662
                                      
                Embedded Hash   SHA2: 7F54083493EB6B06234CFC5266E538E7
                                      .....
                                      .....
                                      0B17572E9A33735ADCEE26A4E3FDB662
                                      
                CCO Hash        MD5 : 966D4092FA8F5F2E0F74BDCF46511CF7
                Digital signature successfully verified in file usbflash0:/c3900-universalk9-mz.SSB
                

                The new special image file with a new special key is copied to the image storage area in the router (usbflash0:) and the signature of the image is verified successfully.

                Router# upgrade rom-monitor file usbflash0:C3900_PRIV_RM2.srec.SSB
                Platform Field Upgradeable ROMMON LOAD test 
                ___________________________________________ 
                RSA Signature Verification Passed ...
                ROM: Digitally Signed Development Software
                 
                This command will result in a  'power-on reset' of the router! 
                Continue? [yes/no]: yes
                ROMMON image upgrade in progress.
                 
                Erasing boot flash eeeeeeeeeeeeeeeeeeeeeeee
                Programming boot flash ........................
                Now Reloading
                FPGA System Reset Fail; Performing IOCTRL System reset
                 
                System Bootstrap, Version 15.0(1r)M3, RELEASE SOFTWARE (fc1)
                Technical Support: http://www.cisco.com/techsupport
                Copyright (c) 2009 by cisco Systems, Inc.
                 
                Total memory size = 1024 MB - DIMM0 = 512 MB, DIMM1 = 512 MB
                 
                 Running new upgrade for first time
                 
                System Bootstrap, Version 12.4(20090921:163953) [image-rommon 152], DEVELOPMENT SOFTWARE
                Copyright (c) 1994-2009 by cisco Systems, Inc.
                 
                Total memory size = 1024 MB - DIMM0 = 512 MB, DIMM1 = 512 MB
                Field Upgradeable ROMMON Integrity test 
                _______________________________________ 
                ROM: Digitally Signed Development Software
                CISCO3945 with CISCO3900-MPE140 with 1048576 Kbytes of main memory
                Main memory is configured to 72/72(dimm 0/1) bit mode with ECC enabled
                Upgrade ROMMON initialized
                program load complete, entry point: 0x4000000, size: 0x3f520
                Continue to reload the same Production image
                

                The ROMmon file is upgraded to the new ROMmon file in the router.

                Router# software authenticity key revoke special 
                Finding the new special key in the key storage
                Validating running image...
                Revoking keys with version less than B
                Validating upgradable rommon...
                Scanning the keys in Primary
                Revoking the key with version A...e.Success
                Scanning the keys in Backup
                Revoking the key with version A...e.Success
                Done!
                 
                Router#
                *Mar  8 10:29:17.219 PST: %DIGISIGN-4-DEV_IMAGE: Upgradable rommon software signed using special key version B
                

                The old special key (Rev A) is revoked from the primary and backup key storage areas.

                Enabling Debugging of Digitally Signed Cisco Software Image Key Information Example

                The following example shows how to enable debugging of software authentication events relating to key information for digitally signed Cisco software:

                Router# debug software authenticity key
                

                Additional References

                The following sections provide references related to the Digitally Signed Cisco Software feature.

                Related Documents

                Related Topic

                Document Title

                Overview of Cisco IOS software activation

                Cisco IOS Software Activation Conceptual Overview

                Commands related to Cisco IOS software activation

                Cisco IOS Software Activation Tasks and Commands

                Standards

                Standard

                Title

                None

                --

                MIBs

                MIB

                MIBs Link

                No new or modified MIBs are supported by this feature.

                To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

                http:/​/​www.cisco.com/​go/​mibs

                RFCs

                RFC

                Title

                None

                --

                Technical Assistance

                Description

                Link

                The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

                To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

                Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

                http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

                Feature Information for Digitally Signed Cisco Software

                The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

                Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

                Table 5 Feature Information for Digitally Signed Cisco Software

                Feature Name

                Releases

                Feature Information

                Digitally Signed Cisco Software

                15.0(1)M, 15.0(1)M2, 15.1(1)T, Cisco IOS XE_3.1.0SG

                The Digitally Signed Cisco Software feature describes how to identify digitally signed Cisco software, gather software authentication information related to digitally signed images, and perform key revocation. Digitally Signed Cisco software is software that is digitally signed using secure asymmetrical (public-key) cryptography.

                In Cisco IOS Release 15.0(1)M, this feature was introduced on the Cisco 1941, 2900, and 3900 routers.

                This feature was integrated into the Cisco IOS Release 15.1(1)T.

                This feature was integrated in Cisco IOS XE Release 3.1.0.SG for the Catalyst 4500 E+Series switches.

                The following commands were introduced or modified: debug software authenticity, show software authenticity file, show software authenticity keys, show software authenticity running.

                Key Revocation Feature Support

                15.0(1)M2, 15.1(1)T

                Key revocation feature support was added. Key revocation removes a key from a platform’s key storage. A platform can host a production or special image, and a production key (from a production image) or special key (from a special image) may be revoked during key revocation.

                The following section provides information about this feature:

                • Digitally Signed Cisco Software Key Revocation and Replacement

                This feature was integrated into the Cisco IOS Release 15.1(1)T.

                The following commands were introduced or modified: debug software authenticity, show software authenticity upgrade-status, software authenticity key add, software authenticity key revoke, upgrade rom-monitor file.