It was arguably the most complex hand operated cipher ever seen. Although certainly not as complex or secure as modern computer operated stream ciphers or block ciphers, in practice it resisted all attempts at cryptanalysis from its discovery in 1953 until Hayhanen's defection in 1957.
The VIC cipher has several components, including a base 10 lagged Fibonacci generator, a straddling checkerboard, and a disrupted double transposition. Until the discovery of VIC, it was generally thought that a double transposition alone was the most complex cipher an agent could practically use in the field.
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