| crypto | Package crypto collects common cryptographic constants. |
| crypto/ecdsa | Package ecdsa implements the Elliptic Curve Digital Signature Algorithm, as defined in [FIPS 186-5]. |
| crypto/elliptic | Package elliptic implements the standard NIST P-224, P-256, P-384, and P-521 elliptic curves over prime fields. |
| crypto/rand | Package rand implements a cryptographically secure random number generator. |
| crypto/rsa | Package rsa implements RSA encryption as specified in PKCS #1 and RFC 8017. |
| crypto/x509 | Package x509 implements a subset of the X.509 standard. |
| encoding/pem | Package pem implements the PEM data encoding, which originated in Privacy Enhanced Mail. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| io/ioutil | Package ioutil implements some I/O utility functions. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| path/filepath | Package filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths. |