Чего только не узнаешь...

https://en.wikipedia.org/wiki/Russian_copulation
In cryptography, Russian copulation is a method of rearranging plaintext before encryption so as to conceal stereotyped headers, salutations, introductions, endings, signatures, etc.
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The English phrase suggests that it originally came from an observation about Russian cryptographic practice. However, the technique is generally useful and neither was, nor is, limited to use by Russians.