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.TH SHA1CDSUM "1" "December 2020" "sha1collisiondetection" "User Commands"
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.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.47.16.
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.TH SHA1CDSUM "1" "December 2020" "sha1cdsum 0.2.3" "User Commands"
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.SH NAME
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sha1cdsum \- SHA\-1 Collision Detection
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sha1cdsum \- SHA-1 digests with collision detection
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.SH DESCRIPTION
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sha1cdsum does a SHA\-1 cryptographic digest, but diverges from SHA\-1
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when it encounters the most common forms of attack against the
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algorithm's collision resistance.
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sha1cdsum 0.2.3
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Print or check SHA1 (160\-bit) checksums with collision detection.
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.SS "USAGE:"
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.IP
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sha1cdsum [FLAGS] [files]...
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.SS "FLAGS:"
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.TP
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\fB\-b\fR, \fB\-\-binary\fR
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read in binary mode
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.TP
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\fB\-c\fR, \fB\-\-check\fR
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read SHA1 sums from the FILEs and check them
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.TP
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\fB\-h\fR, \fB\-\-help\fR
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Prints help information
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.TP
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\fB\-\-tag\fR
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create a BSD\-style checksum
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.TP
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\fB\-t\fR, \fB\-\-text\fR
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read in text mode
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.TP
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\fB\-V\fR, \fB\-\-version\fR
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Prints version information
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.TP
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\fB\-z\fR, \fB\-\-zero\fR
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end each output line with NUL, not newline, and disable file name escaping
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.TP
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\fB\-\-ignore\-missing\fR
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don't fail or report status for missing files
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.TP
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\fB\-\-quiet\fR
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don't print OK for each successfully verified file
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.TP
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\fB\-\-status\fR
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don't output anything, status code shows success
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.TP
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\fB\-\-strict\fR
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exit non\-zero for improperly formatted checksum lines
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.TP
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\fB\-w\fR, \fB\-\-warn\fR
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warn about improperly formatted checksum lines
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.SS "ARGS:"
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.TP
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<files>...
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Input file(s). With no FILE, or when FILE is \-, read standard input
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.PP
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When such an attack is detected, it produces a different digest and
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indicates that a collision block was observed.
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.SS USAGE
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.B sha1cdsum
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reads and calculates over data it receives on standard input, and
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ignores all command line options. But see the WARNING below about
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interface stability.
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.SS EXAMPLE
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.nf
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\f[C]
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$ sha1cdsum < /dev/null
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this is a stub implementation!
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da39a3ee5e6b4b0d3255bfef95601890afd80709
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$ zcat /usr/share/doc/sha1cdsum/examples/shattered-1.pdf.gz | sha1cdsum
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this is a stub implementation!
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*coll* e1761773e6a35916d99f891b77663e6405313587
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$
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\f[R]
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.fi
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.SS WARNING
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The API for this command is unstable and likely to change! See
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https://gitlab.com/sequoia-pgp/sha1collisiondetection/-/issues/2 for details.
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.SS SEE ALSO
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The last five options are useful only when verifying checksums.
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.PP
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The sums are computed using Marc Stevens' modified SHA1 that detects
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collision attacks. When checking, the input should be a former output
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of this program. The default mode is to print a line with checksum, a
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space, a character indicating input mode ('*' for binary, ' ' for text
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or where binary is insignificant), and name for each FILE.
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.PP
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If a collision is detected, '*coll*' is printed in front of the file
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name.
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.PP
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Note: There is no difference between binary mode and text mode on GNU
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systems.
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.PP
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This program implements the same interface as coreutils' sha1sum,
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modulo error messages printed to stderr, handling of non\-UTF8
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filenames, and bugs.
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.SH "SEE ALSO"
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.BR https://shattered.io/
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.PP
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.BR https://sha\-mbles.github.io/
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