Hi Rene,
I totally agree with your observations. Vignère presented its cipher in a concise, complete and clear way and that makes it possible to fully understand its properties.
I am more puzzled by the distance cipher illustrated here:
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The 7 characters example does not show how the whole cipher is supposed to work. Also, T is encoded as yqo1, E is encoded as dqo1. But while y.qo appears consecutively in the cipher text, E is rendered as dy.qo, with the additional symbol y inserted in the sequence. I must be misunderstanding something.
Also, I don't understand how the sequence A S T should be encoded. I am leaving out nulls and representing 'qo' as 'q' (I understand that qo is treated as a single symbol?).
The encoding should be: kk2 kk3 yq1
but I am not sure how this should be handled. Something like:
k k . k y . q k
doen't work, since one gets kk4 instead of kk3.
The alternative
k k . k y . k q
fixes kk3 but breaks yq1.
In general, this system seems to be quite complex to encode and decode. Anyway, I don't think that distance encoding decreases entropy or makes repeating words more likely. Of course, nulls (if added with fixed criteria, rather than randomly as effective cryptography requires) and even more so verbose elements (e.g. "qo" as a single symbol) do lower entropy. A cipher that makes large use of distance 1 sequences basically is a verbose cipher (e.g. encoding S as y.qo) and typically would reduce entropy, but I don't see the added value of the complexity of a proper distance cipher like this.
I totally agree with your observations. Vignère presented its cipher in a concise, complete and clear way and that makes it possible to fully understand its properties.
I am more puzzled by the distance cipher illustrated here:
You are not allowed to view links. Register or Login to view.
The 7 characters example does not show how the whole cipher is supposed to work. Also, T is encoded as yqo1, E is encoded as dqo1. But while y.qo appears consecutively in the cipher text, E is rendered as dy.qo, with the additional symbol y inserted in the sequence. I must be misunderstanding something.
Also, I don't understand how the sequence A S T should be encoded. I am leaving out nulls and representing 'qo' as 'q' (I understand that qo is treated as a single symbol?).
The encoding should be: kk2 kk3 yq1
but I am not sure how this should be handled. Something like:
k k . k y . q k
doen't work, since one gets kk4 instead of kk3.
The alternative
k k . k y . k q
fixes kk3 but breaks yq1.
In general, this system seems to be quite complex to encode and decode. Anyway, I don't think that distance encoding decreases entropy or makes repeating words more likely. Of course, nulls (if added with fixed criteria, rather than randomly as effective cryptography requires) and even more so verbose elements (e.g. "qo" as a single symbol) do lower entropy. A cipher that makes large use of distance 1 sequences basically is a verbose cipher (e.g. encoding S as y.qo) and typically would reduce entropy, but I don't see the added value of the complexity of a proper distance cipher like this.