/**
 * PEM Format Utilities
 *
 * Utilities for working with PEM-formatted cryptographic keys.
 * Issue #1374
 */
/**
 * Check if a string is in valid PEM format
 *
 * PEM format requires:
 * - A BEGIN header with a type (e.g., "-----BEGIN PUBLIC KEY-----")
 * - Base64-encoded content
 * - An END footer with matching type (e.g., "-----END PUBLIC KEY-----")
 *
 * @param input - String to check
 * @returns true if the string is valid PEM format, false otherwise
 */
export declare function isPemFormat(input: string): boolean;
/**
 * Extract the type from a PEM-formatted string
 *
 * For example, extracts "PUBLIC KEY" from:
 * -----BEGIN PUBLIC KEY-----
 * ...
 * -----END PUBLIC KEY-----
 *
 * @param pem - PEM-formatted string
 * @returns The type string (e.g., "PUBLIC KEY", "PRIVATE KEY"), or null if not valid PEM
 */
export declare function extractPemType(pem: string): string | null;
/**
 * Convert PEM-formatted string to raw bytes
 *
 * Extracts the base64 content from between the PEM headers and decodes it.
 *
 * @param pem - PEM-formatted string
 * @returns Raw bytes as Uint8Array
 * @throws Error if the input is not valid PEM format
 */
export declare function pemToBytes(pem: string): Uint8Array;
/**
 * Convert raw bytes to PEM format
 *
 * Encodes the bytes as base64 and wraps with PEM headers.
 * Base64 content is wrapped at 64 characters per line per RFC 7468.
 *
 * @param bytes - Raw bytes to encode
 * @param type - PEM type (e.g., "PUBLIC KEY", "PRIVATE KEY")
 * @returns PEM-formatted string
 */
export declare function bytesToPem(bytes: Uint8Array, type: string): string;
/**
 * Format a key fingerprint for display
 *
 * Converts to uppercase and groups into 4-character blocks separated by spaces.
 * For example: "abcd1234efgh5678" becomes "ABCD 1234 EFGH 5678"
 *
 * @param fingerprint - Raw fingerprint string (typically 40 hex characters)
 * @returns Formatted fingerprint string
 */
export declare function formatFingerprint(fingerprint: string): string;