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Beginner question - hex keys

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JohnFish
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PostPosted: Wed Feb 08, 2006 1:45 pm    Post subject: Beginner question - hex keys Reply with quote

Hi guys. I have taken a security and cryptography module this year in Uni. I have understood everything ok but one very important thing

When you say "we have a 16(say) bit encryption system", I though 16 but of plain text, but it seems that it might be 16 bit of hex strings.

1) What is the general case?
2) How can you convert a say 16-bit hex string to plain text?

Thanks in advance
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PostPosted: Wed Feb 08, 2006 4:26 pm    Post subject: Reply with quote

hi,

When we say bit, its in binary or base 2.
When we say hexadecimal, it is in base 16.
One hexadecimal digit is 4 bits.

For conversion from hex to binary pls see this

When we want to convert binary to plain text(which i assume you mean ASCII) there is an ASCII look up table that you can use.

Cheers.
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JohnFish
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PostPosted: Wed Feb 08, 2006 7:12 pm    Post subject: Reply with quote

Maybe I wasnt clear.

Right when we say "this is based on 16-bit encryption" obviously these are bits but when you write the key you write it as text. 16-bits in text is 2 chars. And then follows the previous question
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PostPosted: Thu Feb 09, 2006 2:01 pm    Post subject: Reply with quote

hi,


If your key is alpha-numeric,it is usually ASCII encoded. Then it means that each ASCII characeter is 8 bits. So, if your key is 2 characters, look up the ASCII Table and find their decimal representation(i.e base 10). Next convert it to binary(base 2) and concatenate the two binary blocks in the same order as you wrote down your character key. Now you can convert it to hexadecimal as described earlier.

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PostPosted: Sat Feb 11, 2006 1:12 am    Post subject: Reply with quote

"X-bit encryption" refers to the size of the key being used for encryption. Since all text is translated into binary sooner or later, whether the bits start as "text" or "hex" is irrelevent, as they will always end in binary/hex.
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