Binary-to-text Encoding - Encoding Plain Text

Encoding Plain Text

Binary-to-text encoding methods are also used as a mechanism for encoding plain text. For example:

• Some systems have a more limited character set they can handle; not only are they not 8-bit clean, some can't even handle every printable ASCII character.
• Other systems have limits on the number of characters that may appear between line breaks, such as the "1000 characters per line" limit of some SMTP software, as allowed by RFC 2821.
• Still others add headers or trailers to the text.
• A few poorly-regarded but still-used protocols use in-band signaling, causing confusion if specific patterns appear in the message. The best-known is the string "From " (including trailing space) at the beginning of a line used to separate mail messages in the mbox file format.

By using a binary-to-text encoding on messages that are already plain text, then decoding on the other end, one can make such systems appear to be completely transparent. This is sometimes referred to as 'ASCII armoring'. For example, the ViewState component of ASP.NET uses base64 encoding to safely transmit text via HTTP POST.