^start of line
.*any Unicode character (except for line terminators), repeated any number of times
\ba Unicode word boundary
RSA SHA256:the literal text RSA SHA256: (case sensitive) .*any Unicode character (except for line terminators), repeated any number of times
Non-Capturing Group(?:\n.*){3} {3}repeats the group contents below exactly 3 times:
\na line-feed (newline) character (ASCII 10)
.*any Unicode character (except for line terminators), repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string