The .htm.crypt.exe files are Windows executables, but they are at the same time ZIP files that can be decompressed with any ZIP utility. They are provided especially for users of non-Windows platforms. Please don't send me mail asking for the key, because I cannot and will not check the authenticity of your mail. Please don't send me mail asking for the key, because I cannot and will not check the authenticity of your mail. New issues appear here on the 15th of March, June, September, and December.
Key length is a consideration.
If somebody wanted to crack the encryption, only a brute force method would work, assuming that the encryption algorithm doesn't contain any loopholes. The algorithms used here do not contain any known loopholes. Supposing that my key consists of only a few letters, upper or lower case, each letter represents about 5 to 6 bits of useful information. Brute force methods are currently safe from about 70 bits upwards, because brute force methods take too much time with sufficiently long keys. Therefore my recommendation is to use mixed case letter keys of at least 14 characters if high security is required, or to use keys containing at least one special character with a total length of at least 10 characters.