| bytes | Package bytes implements functions for the manipulation of byte slices. |
| crypto/aes | Package aes implements AES encryption (formerly Rijndael), as defined in U.S. Federal Information Processing Standards Publication 197. |
| crypto/cipher | Package cipher implements standard block cipher modes that can be wrapped around low-level block cipher implementations. |
| crypto/rand | Package rand implements a cryptographically secure random number generator. |
| errors | Package errors implements functions to manipulate errors. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| io | Package io provides basic interfaces to I/O primitives. |