Deciphering or decoding: reading and interpreting a code, obscure text, or difficult writing to reveal its meaning.
古い手紙を解読して歴史の手がかりを見つけた。
We deciphered the old letter and found clues to the history.
暗号を解読するために専門家を呼んだ。
We called in an expert to decode the cipher.
手書きのメモは読みにくくて解読に苦労した。
The handwritten note was hard to read and difficult to decipher.