![how to encode a message i a picture how to encode a message i a picture](https://c2.staticflickr.com/2/1321/5104672891_e9bbb211b8_b.jpg)
It has to convert the 8-bit text to 7-bit hex codes, which it does by essentially borrowing the remaining bit at the end of every byte. Each two-character code, called a hex code, is one 8-bit chunk, and together it spells “I love you”.īut this is actually not how the message is stored on her phone. Spacebar (notice it’s at the intersection of 2x and x0 above) = “I” (notice it’s at the intersection of 4x and x9 above) = So there my wife is, typing “I love you” into a text message, all the while the phone converts those letters into this 7-bit encoding scheme, called GSM-7. (A bit like the miracle of Hanukkah, if you ask me.) But assuming people will never use those symbols in text messages (a poor assumption, to be sure), this allowed Hillebrand and his colleagues to stuff 160 characters into a 140-byte space, which in turn fit neatly into a 279-byte SS7 signal: exactly the number of characters they claim to have discovered was the perfect length of a message. To squeeze an alphabet down to 7 bits, you need to remove some possible characters: the 1/2 symbol (½), the degree symbol (°), the pi symbol (π), and so on. Part of it needs to let the cell tower know “hey, this is a message, not a call, don’t ring the phone!”.īy the time Hillebrand and his team finished cramming all the necessary contextual bits into the 279-byte signal, they were left with only enough space for 140 characters at 1 byte (8 bits) a piece, or 1,120 bits.īut what if they could encode a character in only 7 bits? At 7 bits per character, they could squeeze 160 (1,120 / 7 = 160) characters into each SMS, but those extra twenty characters demanded a sacrifice: fewer possible letters.Īn 8-bit encoding allows 256 possible characters: lowercase ‘a’ takes up one possible space, uppercase ‘A’ another space, a period takes up a third space, an symbol takes up a fourth space, a line break takes up a fifth space, and so on up to 256. Part of that 279-byte signal needs to contain your phone number, and part of it needs to contain my phone number.
![how to encode a message i a picture how to encode a message i a picture](https://s2.studylib.net/store/data/014314248_1-11a98eb7cf68a0ef3e77454529984a7e-768x994.png)
Unfortunately, getting messages across the SS7 protocol isn’t a simple matter of sending 2,232 (that’s 279 bytes at 8 bits each) 0s or 1s through radio signals from my phone to yours. A byte is eight bits (each bit is a 0 or 1), and in common encodings, a single letter is equivalent to eight 0s and 1s in a row. Normally, 279 bytes equals 279 characters.