字符串base64加密、解密

//base64加密(字符串经过base64加密之后得到的新的字符串)
NSData *data =   
  [@"iOS Developer Tips" dataUsingEncoding:NSUTF8StringEncoding];

NSString *base64Encoded = [data base64EncodedStringWithOptions:0];

//base64解密(base64加密的字符串经过base64解密之后得到的新的字符串)

NSData *nsdataDecoded = [base64Data initWithBase64EncodedString:base64Encoded options:0];
 
NSString *str = [[NSString alloc] initWithData:nsdataDecoded encoding:NSUTF8StringEncoding];