Chinese telegraph code, but use UTF8 as a fallback.
CTC is the shorthand for "Chinese Telegraph Code".
It compiles most of the common characters and assigns them a number.
For example, character 汉 is numbered 3352.
This is a more compact way to index Chinese:
It only uses two bytes (actually it's only 0000 to 9999),
while UTF-8 uses three bytes on average.
While UTF-8 is generally the best option to handle all kinds of characters, when talking about encoding along with a limitation on length, CTC becomes useful.
This program is written for encoding text on postcards, while we don't want to deal with encrypted data represented in base58, but still want some level of privacy. So this program encodes the Chinese into CTC, and if there is a missing character, it uses either raw UTF-8 or compressed UTF-8 to encode.
Handwriting and typing numbers are much easier than base64/58.
The design is: when writing postcards, I encode the text either from cli options,
or files, or from stdin, then it spills out a bunch of numbers, and I just need
to write them on the postcard.
When someone got the postcard, he can type in the numbers and the program will print out the decoded message.
The program is built using jlink with zulu 21 jdk, so technically you don't need
a Java runtime installed on your pc.
Download the correct build for your usage and invoke ./ctc, everything should be fine.
There is no package published to use this codec as a dependency. I didn't write to dependency, I didn't test, so I don't want to people use it and accidentally cause some disaster. You can try with the jitpack, but I won't ensure the result.
If this demand is popular, create an issue and I will work on it to publish as a dependency
You can encode text from the cli option, file, and stdin.
./ctc encode -t "天匠染青红，花腰呈袅娜。"
./ctc encode -f message.txt
echo "天匠染青红，花腰呈袅娜。" | ./ctc encode -c UTF-8The -t <text> option will omit the -f <file> if they are both specified.
When using the stdin, you need to manually tell the program you're done by inputting
EOF on a new line.
You can change the EOF to something else using --eof=EOT, now you can use EOT
instead of EOF.
You can also change how many codes are printed in one line.
But do be aware this is limited by your terminal width, if it's longer than the width, it will wrap.
By default, it's fit your terminal.
You can change it by option -w 6, now you have six codes per line.
When using stdin input, there is some issue with the charset on Windows.
By default, the program uses UTF-8 to read and write everything.
But on windows, it will use GBK if the default locale is zh-CN;
or use BIG5 if the default locale is zh-TW.
If you don't want this feature, you can use -c UTF-8 to force the program to
use UTC-8 charset.
Do verify the program output before you write numbers to your postcard. Sometimes the charset issue can mess you up if you don't check the decoded result.
It's basically the same, but much simpler. When decoding, the program will print everything using UTF-8, which most terminals are ok, even on windows.
For decoding, there are only three options: -t, -f and --eof.
You can type any character, and the program will ignore them and only take the digits. So don't worry if you accidentally typed a letter or something. Keep typing numbers and you're good.
./ctc decode -t "1131, 0561, 2676, 7230, 4767, 9976, 5363, 5212, 0701, 5934, 1226, 9975"Starting from v0.1.0, I added a Transposition Cipher using VMPC random generator.
It supports symmetric encryption (offers only the -k string option) and
asymmetric encryption (offering both -k string and --dh hex) to use X25519 ECDH.
When using symmetric encryption, the key from -k key will be encoded using UTF-8
and apply SH3-256.
The result hash will be used as the seed of VMPC generator.
When using asymmetric encryption, the key will be encoded by UTF-8 and apply SHA3-256. Then use is as our private key to perform X25519 ECDH, the result will be hashed by SHA3-256, and the hash will be used as the encryption key.
Use ./ctc pubkey key to calculate the public key when using -k key.
The encryption is based on Transposition Cipher.
The implementation is #randomize and #derandomize in Utils.kt
One time of randomization is not safe.
So you can use -n to set the iteration amount.
By default, it's 1.2 million times.
There is some internal processing beyond simply lookup the table and do the substitution. The CTC is scraped from https://en.wiktionary.org/wiki/Appendix:Chinese_telegraph_code/Mainland_1983.
Before starting encoding characters, we need to replace some text for shorter codes:
- new lines (
\n) are replaced by〷(code 9999) - text like
10日will be replaced by the char㏩(code 9910)
This will save some code and will be transparent for user. When decoding, reversed processing will be applied to make sure the decoded text is looking normal.
When there is an unknown character, it will save to the buffer and encode them in batches.
For example, when encoding 大家好，my name is XXX。, the unknown buffer will be my name is XXX,
then it will be encoded to utf-8 bytes.
The encoded bytes will be compressed by java.util.zip.Deflater with max level (9),
and the result will be kept if the compress result is shorter than the raw form.
For raw UTF-8 bytes, it will be enclosed with 9992 and 9993, the content
will be representing in 0000 to 9991, like base9992 but all in numbers.
For compressed UTF-8 bytes, it will be enclosed with 9994 and 9995.
The content representation is the same.
Welcome, but I can't guarantee if I accept the pr or not. Open issues as long as you have questions, but I can't guarantee to answer them.
TL;DR: I give no guarantee on the program, unless you pay me.