| crypto/rand | Package rand implements a cryptographically secure random number generator. |
| crypto/sha1 | Package sha1 implements the SHA-1 hash algorithm as defined in RFC 3174. |
| encoding | Package encoding defines interfaces shared by other packages that convert data to and from byte-level and textual representations. |
| encoding/binary | Package binary implements simple translation between numbers and byte sequences and encoding and decoding of varints. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| strconv | Package strconv implements conversions to and from string representations of basic data types. |