How to calculate image hash as a bit sequence of 0's and 1's
in [Matlab]
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From: Walter Roberson on 18 May 2010 10:11 Randima Hettiarachchi wrote: > Thanks a lot. But my original challenge was to calculate the hash value > of a given image as a bit sequence by using a standard encryption > algorithm like MD5, MD4 or SHA. It is much appreciated if you can > provide some clues on that. You mean like the Matlab File Exchange contribution Compute hash using MD2, MD5, SHA-1, SHA-256, SHA-384, or SHA-512 by Michael Kleder ?
From: Randima Hettiarachchi on 18 May 2010 11:16 Walter Roberson <roberson(a)hushmail.com> wrote in message <HexIn.11217$wV.2695(a)newsfe11.iad>... > Randima Hettiarachchi wrote: > > > Thanks a lot. But my original challenge was to calculate the hash value > > of a given image as a bit sequence by using a standard encryption > > algorithm like MD5, MD4 or SHA. It is much appreciated if you can > > provide some clues on that. > > You mean like the Matlab File Exchange contribution > Compute hash using MD2, MD5, SHA-1, SHA-256, SHA-384, or SHA-512 > > by Michael Kleder > > ? Exactly. The only problem I experienced with the above mentioned files shared by Michael Kleder is that those were not implemented to accept images as input to the function. Of course there is no point in feeding pixel values (gray level) one by one as the input to the above encryption algorithms. Because the image hash should be a representative of the whole original image.
From: Walter Roberson on 18 May 2010 11:21 Randima Hettiarachchi wrote: > Walter Roberson <roberson(a)hushmail.com> wrote in message > <HexIn.11217$wV.2695(a)newsfe11.iad>... >> Randima Hettiarachchi wrote: >> >> > Thanks a lot. But my original challenge was to calculate the hash >> value > of a given image as a bit sequence by using a standard >> encryption > algorithm like MD5, MD4 or SHA. It is much appreciated if >> you can > provide some clues on that. >> >> You mean like the Matlab File Exchange contribution >> Compute hash using MD2, MD5, SHA-1, SHA-256, SHA-384, or SHA-512 >> >> by Michael Kleder >> >> ? > > Exactly. The only problem I experienced with the above mentioned files > shared by Michael Kleder is that those were not implemented to accept > images as input to the function. But that's okay, because I showed you how to convert the image into a bit stream.
From: Randima Hettiarachchi on 18 May 2010 12:45 Walter Roberson <roberson(a)hushmail.com> wrote in message <pgyIn.16948$Ak3.5716(a)newsfe16.iad>... > Randima Hettiarachchi wrote: > > Walter Roberson <roberson(a)hushmail.com> wrote in message > > <HexIn.11217$wV.2695(a)newsfe11.iad>... > >> Randima Hettiarachchi wrote: > >> > >> > Thanks a lot. But my original challenge was to calculate the hash > >> value > of a given image as a bit sequence by using a standard > >> encryption > algorithm like MD5, MD4 or SHA. It is much appreciated if > >> you can > provide some clues on that. > >> > >> You mean like the Matlab File Exchange contribution > >> Compute hash using MD2, MD5, SHA-1, SHA-256, SHA-384, or SHA-512 > >> > >> by Michael Kleder > >> > >> ? > > > > Exactly. The only problem I experienced with the above mentioned files > > shared by Michael Kleder is that those were not implemented to accept > > images as input to the function. > > But that's okay, because I showed you how to convert the image into a > bit stream. Sir, do you recommend to feed the image pixel by pixel to the encryption algorithm or just to use the matrix created by using dec2bin() as the image hash?
From: Walter Roberson on 18 May 2010 14:21
Randima Hettiarachchi wrote: > Walter Roberson <roberson(a)hushmail.com> wrote in message > <pgyIn.16948$Ak3.5716(a)newsfe16.iad>... >> Randima Hettiarachchi wrote: >> > Walter Roberson <roberson(a)hushmail.com> wrote in message > >> <HexIn.11217$wV.2695(a)newsfe11.iad>... >> >> Randima Hettiarachchi wrote: >> >> >> >> > Thanks a lot. But my original challenge was to calculate the hash >> >> value > of a given image as a bit sequence by using a standard >> >> encryption > algorithm like MD5, MD4 or SHA. It is much appreciated if >> >> you can > provide some clues on that. >> >> >> >> You mean like the Matlab File Exchange contribution >> >> Compute hash using MD2, MD5, SHA-1, SHA-256, SHA-384, or SHA-512 >> >> >> >> by Michael Kleder >> >> >> >> ? >> > > Exactly. The only problem I experienced with the above mentioned >> files > shared by Michael Kleder is that those were not implemented to >> accept > images as input to the function. >> >> But that's okay, because I showed you how to convert the image into a >> bit stream. > > Sir, do you recommend to feed the image pixel by pixel to the encryption > algorithm or just to use the matrix created by using dec2bin() as the > image hash? If you examine Chris Rodgers' comment http://www.mathworks.com/matlabcentral/fileexchange/8944-compute-hash-using-md2-md5-sha-1-sha-256-sha-384-or-sha-512 then I think it probable that his update would also be suitable for handling complete images, with no need to send the image bit-by-bit. The matrix created by dec2bin() is *not* suitable as the hash itself. |