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using iotop to find disk usage hogs

using iotop to find disk usage hogs






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Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

Workaround and fixes for the current Core Dump Handling vulnerability affected kernels






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April, 26th. 2006:

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Section: OpenSSL (1)
Updated: 2015-01-20
Index Return to Main Contents


dgst, sha, sha1, mdc2, ripemd160, sha224, sha256, sha384, sha512, md2, md4, md5, dss1 - message digests  


openssl dgst [-sha|-sha1|-mdc2|-ripemd160|-sha224|-sha256|-sha384|-sha512|-md2|-md4|-md5|-dss1] [-c] [-d] [-hex] [-binary] [-r] [-hmac arg] [-non-fips-allow] [-out filename] [-sign filename] [-keyform arg] [-passin arg] [-verify filename] [-prverify filename] [-signature filename] [-hmac key] [-non-fips-allow] [-fips-fingerprint] [file...]

openssl [digest] [...]  


The digest functions output the message digest of a supplied file or files in hexadecimal. The digest functions also generate and verify digital signatures using message digests.  


print out the digest in two digit groups separated by colons, only relevant if hex format output is used.
print out BIO debugging information.
digest is to be output as a hex dump. This is the default case for a ``normal'' digest as opposed to a digital signature. See NOTES below for digital signatures using -hex.
output the digest or signature in binary form.
output the digest in the ``coreutils'' format used by programs like sha1sum.
-hmac arg
set the HMAC key to ``arg''.
Allow use of non FIPS digest when in FIPS mode. This has no effect when not in FIPS mode.
-out filename
filename to output to, or standard output by default.
-sign filename
digitally sign the digest using the private key in ``filename''.
-keyform arg
Specifies the key format to sign digest with. The DER, PEM, P12, and ENGINE formats are supported.
-engine id
Use engine id for operations (including private key storage). This engine is not used as source for digest algorithms, unless it is also specified in the configuration file.
-sigopt nm:v
Pass options to the signature algorithm during sign or verify operations. Names and values of these options are algorithm-specific.
-passin arg
the private key password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
-verify filename
verify the signature using the the public key in ``filename''. The output is either ``Verification OK'' or ``Verification Failure''.
-prverify filename
verify the signature using the the private key in ``filename''.
-signature filename
the actual signature to verify.
-hmac key
create a hashed MAC using ``key''.
-mac alg
create MAC (keyed Message Authentication Code). The most popular MAC algorithm is HMAC (hash-based MAC), but there are other MAC algorithms which are not based on hash, for instance gost-mac algorithm, supported by ccgost engine. MAC keys and other options should be set via -macopt parameter.
-macopt nm:v
Passes options to MAC algorithm, specified by -mac key. Following options are supported by both by HMAC and gost-mac:
Specifies MAC key as alphnumeric string (use if key contain printable characters only). String length must conform to any restrictions of the MAC algorithm for example exactly 32 chars for gost-mac.
Specifies MAC key in hexadecimal form (two hex digits per byte). Key length must conform to any restrictions of the MAC algorithm for example exactly 32 chars for gost-mac.
-rand file(s)
a file or files containing random data used to seed the random number generator, or an EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.
enable use of non-FIPS algorithms such as MD5 even in FIPS mode.
compute HMAC using a specific key for certain OpenSSL-FIPS operations.
file or files to digest. If no files are specified then standard input is used.


To create a hex-encoded message digest of a file:
 openssl dgst -md5 -hex file.txt

To sign a file using SHA-256 with binary file output:
 openssl dgst -sha256 -sign privatekey.pem -out signature.sign file.txt

To verify a signature:
 openssl dgst -sha256 -verify publickey.pem \
 -signature signature.sign \


The digest of choice for all new applications is SHA1. Other digests are however still widely used.

When signing a file, dgst will automatically determine the algorithm (RSA, ECC, etc) to use for signing based on the private key's ASN.1 info. When verifying signatures, it only handles the RSA, DSA, or ECDSA signature itself, not the related data to identify the signer and algorithm used in formats such as x.509, CMS, and S/MIME.

A source of random numbers is required for certain signing algorithms, in particular ECDSA and DSA.

The signing and verify options should only be used if a single file is being signed or verified.

Hex signatures cannot be verified using openssl. Instead, use ``xxd -r'' or similar program to transform the hex signature into a binary signature prior to verification.




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