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#### chisigma

##### Well-known member

- Feb 13, 2012

- 1,704

$\displaystyle c_{n} = p_{n} + k_{n}\ (1)$

... where the sum is modulo some 'large number' N. It is well known that the (1) is 'theoretically secure' if and only if...

a) the sequence $k_{n}$ is 'absolutely random'...

b) the sequence $k_{n}$ is to be use only for a single message...

It is also well known that this solution has many pratical problems, mainly the necessity to have a large number of sequence $k_{n}$ only for have a secure communication between two persons. An idea to overcome that drawback may be to use a $k_{n,m}$ for the message m and a $k_{n,m+1}$ for the message m+1 and in the message m to communicate...

$\displaystyle c_{n,m} = p_{n,m} + k_{n,m},\ h_{n,m}= k_{n,m} + k_{n,m+1}\ (2)$

What is Your opinion regarding the security of this type of cryptosystem?...

Kind regards

$\chi$ $\sigma$