Installation media integrity checking

To verify the correctness of downloaded ISO images you would usually calculate and compare some checksum (digest), for example SHA256, to a reference value obtained from some website.

To make this process easier, the digest can be embedded into the ISO itself.

While this guards against transmission errors it won’t prevent anyone from manipulating the ISO. To ensure authenticity of the ISO image, the embedded meta data can be signed.

Table of Contents

About
Downloads
Technical specification
Usage examples
openSUSE Development

About

checkmedia is a tool to verify installation media. Its counterpart tagmedia creates and embeds the necessary meta data into the ISO image.

The checking functionality is also provided as shared library libmediacheck.so.

The tool set supports openSUSE / SLE ('SUSE') and Fedora / RHEL ('RH') - including their derivatives - media.

The digest data tagmedia creates for RH media is compatible with the implantisomd5 / checkisomd5 tool set.

Downloads

Packages for openSUSE and SLES are built at the openSUSE Build Service. You can grab

official releases or
latest stable versions from my ports project

Technical specification

The digest data is stored in the application specific data in the primary volume descriptor of the ISO. This an area of 512 bytes that are reserved by the ISO9660 standard to be used as applications see fit. The area starts at offset 0x8373 of the ISO9660 file system and is usually filled with spaces.

The data is structured roughly as key = value pairs, separated by semicolons (;).

Here are some examples:

openSUSE

# tagmedia --show openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
check = 1
pad = 150
sha256sum = a722af5e8ff16b07bc38c0971a79f8581016e0d39d3ccc520ac02f6a81f08158
partition = 10432,9135936,c31a435ff7bef3ef3f27575985084060a493227684bd335934d8ca94c85f0a71
signature = 20864

and the corresponding raw data

# tagmedia --export-tags - openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
check=1;pad=150;sha256sum=a722af5e8ff16b07bc38c0971a79f8581016e0d39d3ccc520ac02f6a81f08158;partition=10432,9135936,c31a435ff7bef3ef3f27575985084060a493227684bd335934d8ca94c85f0a71;signature=20864

Fedora

# tagmedia --show Fedora-Server-dvd-x86_64-34-1.2.iso
ISO MD5SUM = 8e80cc6b4a27cf1f76c8f9e665eb22d5
SKIPSECTORS = 15
RHLISOSTATUS = 1
FRAGMENT SUMS = 1c62fb9659fa3637af7088c71c537657e323935cf12d22de58432182cb58
FRAGMENT COUNT = 20
THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!

and the corresponding raw data

# tagmedia --export-tags - Fedora-Server-dvd-x86_64-34-1.2.iso
ISO MD5SUM = 8e80cc6b4a27cf1f76c8f9e665eb22d5;SKIPSECTORS = 15;RHLISOSTATUS=1;FRAGMENT SUMS = 1c62fb9659fa3637af7088c71c537657e323935cf12d22de58432182cb58;FRAGMENT COUNT = 20;THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!

Notes

SUSE
- uses lower-case keys with no spaces around the equal sign (=)
- supported digests are MD5, SHA1, SHA224, SHA256, SHA384, and SHA512
- at least the <digest>sum key must be present
RH
- uses upper-case, with a single space around the equal sign - except for RHLISOSTATUS which must not have spaces around the equal sign
- the only supported digest is MD5
- at least the ISO MD5SUM, SKIPSECTORS, FRAGMENT SUMS, and FRAGMENT COUNT keys must be present
for checkmedia, case does not matter and there can be any number of spaces around the equal sign
for checkisomd5, case does matter and also the acceptable number of spaces is fixed

Digest calculation

The digest is calculated over the whole ISO image with some exceptions:

0x8373-0x8572 (application specific area) is replaced with an empty application specific area (all spaces)
SUSE only
- 0x0000 - 0x01ff (MBR) is replaced by an area with all zeros; this is done to avoid problems with isohybrid images
- if the pad key is set, pad 2 kiB blocks at the end of the ISO are replaced with all zeros
- if a signature is present, the 2 kiB block containing the signature is replaced with an empty signature block (magic string + all zeros)
RH only
- SKIPSECTORS 2 kiB blocks at the end of the ISO are skipped

In addition to the digest over the whole ISO, SUSE can optionally store a digest over a partition (usually the partition containing the installer). This is useful for checking the medium after copying the image to an USB disk.

The format of the partition entry is partition=<startblock>,<blocks>,<digest> - with a block size of 0.5 kiB. <digest> is the same digest type as used for the <digest>sum entry.

RH stores also a 'progressive' digest in the FRAGMENT SUMS key. For this, the image is partitioned into FRAGMENT COUNT roughly equidistant fragments and a 'mini digest' is checked for each fragment. This allows to detect errors early without completing the check of the entire ISO.

The exact algorithm is a bit tricky and is detailed separately below.

Note that the digest over the entire ISO has to be checked in addition since the end of the last fragment does not coincide with the image end.

Fragment digest calculation

This section describes how to calculate the digest stored in the FRAGMENT SUMS field.

FRAGMENT SUMS has a fixed length of 60 chars
FRAGMENT COUNT is the number of fragments; the number of fragments must be an integral divisor of 60; for RH, it must be >= 4 (see below)
FRAGMENT SUMS is made up of FRAGMENT COUNT parts (from left to right) with a length of 60 / FRAGMENT COUNT each

calculate (all integer arithmetic, block size is 2 kiB):

FRAGMENT_SUM_SIZE = 60 / FRAGMENT_COUNT
TOTAL_BYTES = (ISO_BLOCKS - SKIP_SECTORS) << 11
FRAGMENT = TOTAL_BYTES / (FRAGMENT_COUNT + 1)
FRAGMENT_BLOCKS(N) = ((N * FRAGMENT & -0x8000) + 0x8000) >> 11;

the N-th fragment starts at block 0 and has a length of FRAGMENT_BLOCKS(N)
N runs from 1 to FRAGMENT COUNT
for each fragment calculate the digest, taking into account the specifics described above
convert each of the leading FRAGMENT_SUM_SIZE bytes of the binary digest to a single hex digit by choosing the leading char of the hexadecimal representation of the byte; think of sprintf("%x", digest[i])[0]
FRAGMENT_SUM_SIZE should not be larger than the size of the digest used - else there’s not enough data and FRAGMENT SUMS will be shorter than 60; this means FRAGMENT COUNT should be at least 4 (resulting in a FRAGMENT_SUM_SIZE of 15) when MD5 (which has a size of 16 bytes) is used

Notes

the implementation of all this looks much simpler; it will just read 32 kiB blobs and finalize the digest whenever it crosses into a new fragment
the original implementation does the digest calculation before checking the fragment boundary - hence the + 0x8000 in the formalized description above as the 32 kiB buffer has already been added at this point

Here’s an example using the Fedora image from above (0.5 kiB blocks):

# tagmedia --digest md5 -v -v Fedora-Server-dvd-x86_64-34-1.2.iso
iso blocks = 4102876
detected rh style
full blocks = 4102816, fragment bytes = 100030561
fragment  1, blocks   195456: md5 1c0c6a5ac5b34ea8df3a552b9c3bf1ef - 1c6
fragment  2, blocks   390848: md5 2df6bd74166e100c5391e0bed3347672 - 2fb
fragment  3, blocks   586240: md5 9466514b11c38db8b06866ec8e0d8ac8 - 965
fragment  4, blocks   781568: md5 97fbaf84ef507cd6a5252fc7a6786265 - 9fa
fragment  5, blocks   976960: md5 386b3236af93ba0dfb5cd0e5b91bb86a - 363
fragment  6, blocks  1172352: md5 74a6f64e4d5ff6ba37339915ebc11b58 - 7af
fragment  7, blocks  1367680: md5 75008cc3eebffc7a0ce27278ebaaf4a1 - 708
fragment  8, blocks  1563072: md5 83c976c7f0c8a5f6a8ff692493d5b292 - 8c7
fragment  9, blocks  1758464: md5 16cb57a24f96b40a71608a441820bbe7 - 1c5
fragment 10, blocks  1953792: md5 3c076f8c23f6d87a643f9317354d91af - 376
fragment 11, blocks  2149184: md5 5f7eee102db6ae4880053c24045b094f - 57e
fragment 12, blocks  2344576: md5 3f22364d872f86976dbb19ee8cf2b94b - 323
fragment 13, blocks  2539904: md5 9e305dfa6b282781d9817749874cdc3d - 935
fragment 14, blocks  2735296: md5 cffa1252febd54126a7e30098e5865ce - cf1
fragment 15, blocks  2930688: md5 26dc02a13d4c514241d1da19ab4abfc6 - 2d2
fragment 16, blocks  3126080: md5 2bd8ef5f7887abd1f2a95da3b4b33d9e - 2de
fragment 17, blocks  3321408: md5 5c8e46a88df449fd8536f0193ad10b59 - 584
fragment 18, blocks  3516800: md5 03271070cbaf72cd7b14bbd2a095ad0a - 321
fragment 19, blocks  3712192: md5 8729ca3dc084ef9702cd5ce2cf209f36 - 82c
fragment 20, blocks  3907520: md5 b35789e21563f2336bbe8dbc315c855a - b58
ISO MD5SUM = 8e80cc6b4a27cf1f76c8f9e665eb22d5
SKIPSECTORS = 15
RHLISOSTATUS = 0
FRAGMENT SUMS = 1c62fb9659fa3637af7088c71c537657e323935cf12d22de58432182cb58
FRAGMENT COUNT = 20
THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!

Signatures

If the meta data contains a signature (or SIGNATURE) key, the value is the starting block (in 0.5 kiB units) of a 2 kiB area that may contain signing data.

This signature block starts with the magic string 7984fc91-a43f-4e45-bf27-6d3aa08b24cf followed by 28 zero bytes. After that may follow an OpenPGP signature in ASCII armor. The signature is calculated over the 512 bytes of the application specific area.

Here’s an example using the Tumbleweed image from above:

# tagmedia --export-signature - openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iQEVAwUAYSQahLiLL9Q9vcKEAQhNawgAoLq1PcxFDXPv7WkODxyxr/tatoSNOkQt
RdnQNOc/0XFBq0gr3WYmyfHbH2tkirYC6egW/J6ro7AnW9XSkTBXHlgLyamYE8tH
fluKi2xw5Qalv3YKD+6fFWvAF0BL9NSDAXvpRClH6tS9DWTVJ7c0W/sMFMlwwEtj
3GAP7jRLRPqwaL7wKyDnoMb4+umTPqlDNqARh2XXwQ7lnahY5UNzQbmmMQ359Tqq
4JTAueBakpdUoCY6BJt2H/HFUqVaVWa8JPetmfKKVI2HGUaiOzYav7JqVcQXgAQz
WdzM7QJMJuIAr/q3zNlwWLus6xU8hUhzfsRDvkr+BoXAaFWwWpeIpg==
=zvYC
-----END PGP SIGNATURE-----

The raw signature block looks like this:

# tagmedia --show openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso | grep -i signature
signature = 20864
# dd if=openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso bs=512 count=4 skip=20864 status=none | hexdump -C
00000000  37 39 38 34 66 63 39 31  2d 61 34 33 66 2d 34 65  |7984fc91-a43f-4e|
00000010  34 35 2d 62 66 32 37 2d  36 64 33 61 61 30 38 62  |45-bf27-6d3aa08b|
00000020  32 34 63 66 0a 00 00 00  00 00 00 00 00 00 00 00  |24cf............|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  2d 2d 2d 2d 2d 42 45 47  49 4e 20 50 47 50 20 53  |-----BEGIN PGP S|
00000050  49 47 4e 41 54 55 52 45  2d 2d 2d 2d 2d 0a 56 65  |IGNATURE-----.Ve|
00000060  72 73 69 6f 6e 3a 20 47  6e 75 50 47 20 76 31 2e  |rsion: GnuPG v1.|
00000070  30 2e 37 20 28 47 4e 55  2f 4c 69 6e 75 78 29 0a  |0.7 (GNU/Linux).|
00000080  0a 69 51 45 56 41 77 55  41 59 53 51 61 68 4c 69  |.iQEVAwUAYSQahLi|
00000090  4c 4c 39 51 39 76 63 4b  45 41 51 68 4e 61 77 67  |LL9Q9vcKEAQhNawg|
000000a0  41 6f 4c 71 31 50 63 78  46 44 58 50 76 37 57 6b  |AoLq1PcxFDXPv7Wk|
000000b0  4f 44 78 79 78 72 2f 74  61 74 6f 53 4e 4f 6b 51  |ODxyxr/tatoSNOkQ|
000000c0  74 0a 52 64 6e 51 4e 4f  63 2f 30 58 46 42 71 30  |t.RdnQNOc/0XFBq0|
000000d0  67 72 33 57 59 6d 79 66  48 62 48 32 74 6b 69 72  |gr3WYmyfHbH2tkir|
000000e0  59 43 36 65 67 57 2f 4a  36 72 6f 37 41 6e 57 39  |YC6egW/J6ro7AnW9|
000000f0  58 53 6b 54 42 58 48 6c  67 4c 79 61 6d 59 45 38  |XSkTBXHlgLyamYE8|
00000100  74 48 0a 66 6c 75 4b 69  32 78 77 35 51 61 6c 76  |tH.fluKi2xw5Qalv|
00000110  33 59 4b 44 2b 36 66 46  57 76 41 46 30 42 4c 39  |3YKD+6fFWvAF0BL9|
00000120  4e 53 44 41 58 76 70 52  43 6c 48 36 74 53 39 44  |NSDAXvpRClH6tS9D|
00000130  57 54 56 4a 37 63 30 57  2f 73 4d 46 4d 6c 77 77  |WTVJ7c0W/sMFMlww|
00000140  45 74 6a 0a 33 47 41 50  37 6a 52 4c 52 50 71 77  |Etj.3GAP7jRLRPqw|
00000150  61 4c 37 77 4b 79 44 6e  6f 4d 62 34 2b 75 6d 54  |aL7wKyDnoMb4+umT|
00000160  50 71 6c 44 4e 71 41 52  68 32 58 58 77 51 37 6c  |PqlDNqARh2XXwQ7l|
00000170  6e 61 68 59 35 55 4e 7a  51 62 6d 6d 4d 51 33 35  |nahY5UNzQbmmMQ35|
00000180  39 54 71 71 0a 34 4a 54  41 75 65 42 61 6b 70 64  |9Tqq.4JTAueBakpd|
00000190  55 6f 43 59 36 42 4a 74  32 48 2f 48 46 55 71 56  |UoCY6BJt2H/HFUqV|
000001a0  61 56 57 61 38 4a 50 65  74 6d 66 4b 4b 56 49 32  |aVWa8JPetmfKKVI2|
000001b0  48 47 55 61 69 4f 7a 59  61 76 37 4a 71 56 63 51  |HGUaiOzYav7JqVcQ|
000001c0  58 67 41 51 7a 0a 57 64  7a 4d 37 51 4a 4d 4a 75  |XgAQz.WdzM7QJMJu|
000001d0  49 41 72 2f 71 33 7a 4e  6c 77 57 4c 75 73 36 78  |IAr/q3zNlwWLus6x|
000001e0  55 38 68 55 68 7a 66 73  52 44 76 6b 72 2b 42 6f  |U8hUhzfsRDvkr+Bo|
000001f0  58 41 61 46 57 77 57 70  65 49 70 67 3d 3d 0a 3d  |XAaFWwWpeIpg==.=|
00000200  7a 76 59 43 0a 2d 2d 2d  2d 2d 45 4e 44 20 50 47  |zvYC.-----END PG|
00000210  50 20 53 49 47 4e 41 54  55 52 45 2d 2d 2d 2d 2d  |P SIGNATURE-----|
00000220  0a 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000230  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000800

Verification

The signature is verified using the the public keys installed in /usr/lib/rpm/gnupg/keys. Alternatively, pass the public GPG key file to use with the --key-file option to checkmedia.

Extensions

Adding a signature to RH media

Although the standard RH tools (implantisomd5 / checkisomd5) do not support signing the meta data, it is still possible to do it. checkmedia will verify it and checkisomd5 will accept the image as well. So there is no conflict.

The way to do it is to place the signature block in the skipped area. tagmedia will look at the first block in the skipped area when it searches for a signature block and add a SIGNATURE key (upper-case to align with the RH style) to the meta data in this case.

Adding a fragment digest to SUSE media

tagmedia allows to add a RH-style fragment digest also for SUSE media. The calculation uses the same digest that is used for the main ISO checksum and is not limited to MD5.

Usage examples

Checking media

SUSE

# checkmedia openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
        app: openSUSE-Tumbleweed-DVD-x86_64-Build2850.3-Media
   iso size: 4572572 kiB
        pad: 300 kiB
  partition: start 5216 kiB, size 4567968 kiB
   checking: 100%
     result: iso sha256 ok, partition sha256 ok
     sha256: 90b9fdd5f2332ed6728a6a67f8fe78c0b16af4369637bff0e661c507dd5d69eb
  signature: ok
  signed by: openSUSE Project Signing Key <[email protected]>

RH

# checkmedia Fedora-Server-dvd-x86_64-34-1.2.iso
        app: Fedora-S-dvd-x86_64-34
   iso size: 2051438 kiB
       skip: 30 kiB
   checking: 100%
     result: iso md5 ok, fragments md5 ok
        md5: b3c174a7cd4ef9095e46365acba41cbd
  signature: not signed

Notes

the ISO in openSUSE example is signed and the signature was sucessfully verified
the ISO in the Fedora example has additionally a fragments checksum

Creating digest data

SUSE

Let’s take the openSUSE image from above and change the digest to SHA1 and add a RH-like fragment sum:

# tagmedia --clean --digest sha1 --pad 150 --fragments 20 openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
pad = 150
sha1sum = 612df62c3c0c604ae8fe98197c17bff6c0af313e
fragment sums = cda2f8ff1721a96b8a1b9725936784b45a13bfa5d86be8d33166b14c5374cec
fragment count = 20
partition = 10432,9135936,530bcfb94183501626347de64a67061e2c8ba005
signature = 20864

Verifying the ISO now uses SHA1, but the signature is no longer valid:

# checkmedia openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
        app: openSUSE-Tumbleweed-DVD-x86_64-Build2850.3-Media
   iso size: 4572572 kiB
        pad: 300 kiB
  partition: start 5216 kiB, size 4567968 kiB
   checking: 100%
     result: iso sha1 ok, partition sha1 ok, fragments sha1 ok
       sha1: aacd1518d496b938378c95f4ee81ea7d3f82b912
  signature: bad

RH

tagmedia also works with the Fedora image; let’s change the number of fragments:

# tagmedia --clean --digest md5 --fragments 30 Fedora-Server-dvd-x86_64-34-1.2.iso
RHLISOSTATUS = 0
SKIPSECTORS = 15
FRAGMENT SUMS = 769fd46965c792aa2d94e235e9121e4766539c7c532896bef5e2b379afa4
FRAGMENT COUNT = 30
ISO MD5SUM = 8e80cc6b4a27cf1f76c8f9e665eb22d5
THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!

Both checkmedia and checkisomd5 like it:

# checkmedia Fedora-Server-dvd-x86_64-34-1.2.iso
        app: Fedora-S-dvd-x86_64-34
   iso size: 2051438 kiB
       skip: 30 kiB
   checking: 100%
     result: iso md5 ok, fragments md5 ok
        md5: 41cba2ffaacf529e90429bcea4de380b
  signature: not signed

# checkisomd5 --verbose Fedora-Server-dvd-x86_64-34-1.2.iso
Fedora-Server-dvd-x86_64-34-1.2.iso:   8e80cc6b4a27cf1f76c8f9e665eb22d5
Fragment sums: 769fd46965c792aa2d94e235e9121e4766539c7c532896bef5e2b379afa4
Fragment count: 30
Supported ISO: no
Press [Esc] to abort check.
Checking: 100.0%

The media check is complete, the result is: PASS.

It is OK to use this media.

Creating a signature

Let’s continue with the examples from the last section and sign the media with our own key.

# tagmedia --create-signature Testkey openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
# checkmedia --key-file openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso.key openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso
        app: openSUSE-Tumbleweed-DVD-x86_64-Build2850.3-Media
   iso size: 4572572 kiB
        pad: 300 kiB
  partition: start 5216 kiB, size 4567968 kiB
   checking: 100%
     result: iso sha1 ok, partition sha1 ok, fragments sha1 ok
       sha1: 49143cb1e1bd51b6d3d62e5fe0908b97027bfbbb
  signature: ok
  signed by: Testkey Signing Key

Note that tagmedia stored the matching public key part in openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210823-Media.iso.key.

This also works with the Fedora image:

# tagmedia --create-signature Testkey Fedora-Server-dvd-x86_64-34-1.2.iso
# tagmedia Fedora-Server-dvd-x86_64-34-1.2.iso
RHLISOSTATUS = 0
SKIPSECTORS = 15
FRAGMENT SUMS = 769fd46965c792aa2d94e235e9121e4766539c7c532896bef5e2b379afa4
FRAGMENT COUNT = 30
ISO MD5SUM = 8e80cc6b4a27cf1f76c8f9e665eb22d5
THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!
SIGNATURE = 4102816

You can see that tagmedia automatically found a place for the signature block and added a link to it to the meta data.

# checkmedia --key-file Fedora-Server-dvd-x86_64-34-1.2.iso.key Fedora-Server-dvd-x86_64-34-1.2.iso
        app: Fedora-S-dvd-x86_64-34
   iso size: 2051438 kiB
       skip: 30 kiB
   checking: 100%
     result: iso md5 ok, fragments md5 ok
        md5: 5d945293a66a6fb8987dc8b077d5143f
  signature: ok
  signed by: Testkey Signing Key

checkisomd5 also likes it:

# checkisomd5 Fedora-Server-dvd-x86_64-34-1.2.iso
Press [Esc] to abort check.

The media check is complete, the result is: PASS.

It is OK to use this media.

openSUSE Development

To build, simply run make. Install with make install.

Basically every new commit into the master branch of the repository will be auto-submitted to all current SUSE products. No further action is needed except accepting the pull request.

Submissions are managed by a SUSE internal jenkins node in the InstallTools tab.

Each time a new commit is integrated into the master branch of the repository, a new submit request is created to the openSUSE Build Service. The devel project is system:install:head.

*.changes and version numbers are auto-generated from git commits, you don’t have to worry about this.

The spec file is maintained in the Build Service only. If you need to change it for the master branch, submit to the devel project in the build service directly.

Development happens exclusively in the master branch. The branch is used for all current products.

You can find more information about the changes auto-generation and the tools used for jenkis submissions in the linuxrc-devtools documentation.

Name		Name	Last commit message	Last commit date
Latest commit History 77 Commits
obs		obs
tests		tests
.gitignore		.gitignore
COPYING		COPYING
Makefile		Makefile
README.adoc		README.adoc
checkmedia.c		checkmedia.c
checkmedia_man.adoc		checkmedia_man.adoc
digestdemo.c		digestdemo.c
git2log		git2log
md5.c		md5.c
md5.h		md5.h
mediacheck.c		mediacheck.c
mediacheck.h		mediacheck.h
mediacheck.md		mediacheck.md
sha1.c		sha1.c
sha1.h		sha1.h
sha256.c		sha256.c
sha256.h		sha256.h
sha512.c		sha512.c
sha512.h		sha512.h
tagmedia		tagmedia
tagmedia_man.adoc		tagmedia_man.adoc
testmediacheck		testmediacheck
u64.h		u64.h

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Creating digest data

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About

Downloads

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Digest calculation

Fragment digest calculation

Signatures

Verification

Extensions

Adding a signature to RH media

Adding a fragment digest to SUSE media

Usage examples

Checking media

Creating digest data

Creating a signature

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